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The act of manipulating someone psychologically so that they begin to doubt their experience of reality. The phrase comes from the 1938 play Gas Light, in which the protagonist attempts to induce insanity in his wife by constantly questioning or doubting her reports of strange events, such as the dimming of the house's gas lights (which has in fact occurred and is related to the husband's nefarious activities). Her husband must be gaslighting her because she suddenly doubts all the evidence that she's found of his indiscretions. The administration has been accused of gaslighting with its repeated attempts to spread disinformation.

light up

1. To literally brighten or illuminate something. In this usage, "light up" is usually a set phrase. Fireworks lit up the night sky.
2. To become illuminated. In this usage, "light up" is usually a set phrase. The street lamps light up at dusk.
3. To focus a light source on someone or something. In this usage, "light up" is usually a set phrase. The flashlight lit up a stray cat in the bushes.
4. To become noticeably excited or animated at the sight of someone or something. In this usage, "light up" is usually a set phrase. I'm sure she likes you—she just lights up whenever you're around.
5. To cause someone to become noticeably excited or animated. I'm sure she likes you—you just light her up whenever you're around.
6. To light something that can be smoked, such as a cigarette. Please don't light up in my new car—I don't want it to smell like smoke.
7. To ignite something. I used a match to light up the pilot on the stove.
8. To become ignited or begin to burn. In this usage, "light up" is usually a set phrase. The firewood still hasn't lit up—what am I doing wrong?
See also: light, up

light the (blue) touch paper

To do something that instigates or initiates some intense or widespread action or reaction. Primarily heard in UK. Their goal late in the first half seemed to light the blue touch paper for the team, as they have shown much more energy and aggression on the pitch since then. The proposed law has lit the touch paper for activists, who have been gathering people and resources to protest it en masse.
See also: light, paper, touch

light the fuse

To do something that instigates or initiates some intense, dangerous, and widespread action or reaction. Many have accused the leader of lighting the fuse for war with his inflammatory remarks. The law seems poised to light the fuse for protests across the nation should it be passed.
See also: fuse, light

light someone or something up

to shine lights on someone or something. (See also light something up.) We lit Fred up with the headlights of the car. Light up the stage and let's rehearse.
See also: light, up

light something up

1. to light a fire, a gas burner, etc. I lit the kindling up and soon the fire was going. You light up the stove and get dinner going.
2. to light something to smoke, such as a cigarette, pipe, etc. (See also light someone or something up.) She lit the cigarette up and took in a great breath of the smoke. She lit up a cigarette.
See also: light, up

light up

1. to become brighter. Suddenly, the sky lit up like day. The room lit up as the fire suddenly came back to life.
2. [for someone] to become interested and responsive in something. We could tell from the way Sally lit up that she recognized the man in the picture. She lit up when we told her about our team's success.
See also: light, up

light up

1. Become or cause to become more animated or cheerful, as in Her laughter lit up the whole room, or His face lit up when he saw her. This expression transfers physical illumination to human moods. Also see lighten up. [Mid-1700s]
2. Start smoking a cigar, cigarette, or pipe, as in The minute he got outside the church he lit up. [Colloquial; mid-1800s]
See also: light, up

light the fuse

If someone or something lights the fuse, they do something which starts something dangerous or exciting. An outbreak of the virus could light the fuse on the world's next pandemic. This event might have lit the fuse which later led to a depressive breakdown. Note: The fuse referred to here is the type that is used to set off a firework or explosive device.
See also: fuse, light

light the (or a) fuse (or touchpaper)

do something that creates a tense or exciting situation.
The image here is of lighting a fuse attached to gunpowder, fireworks, etc. in order to cause an explosion. A touchpaper , which is used in the same way as a fuse, is a twist of paper impregnated with saltpetre to make it burn slowly.
1998 Times The rejection of global capitalism may light a touchpaper in all those countries battered by the crisis.
See also: fuse, light

light up

1. To illuminate or be illuminated: All the neon signs along the street light up at night.
2. To cause something to illuminate or be illuminated: The morning sun lit up the room. The miners lit their headlamps up and descended into the shaft.
3. To begin to burn: The gas burners lit up on the first try.
4. To cause something to burn; ignite something: I lit up a match and started the fire. I'll get some wood and light a fire up.
5. To ignite and begin smoking something, especially a cigarette, cigar, or pipe: I went out to the porch and lit up a cigar. He lit his pipe up with a match. She took a cigarette from the case and lit up.
6. To become animated or cheerful: The children's eyes lit up when they saw the size of the cake.
7. To cause someone or something to become animated or cheerful: The presence of the movie star lit up the room. He was feeling sad, but the surprise party lit his face up.
See also: light, up
References in periodicals archive ?
People reported no drop in satisfaction with their office lighting, notes James R.
Outdoor lighting is more weather-resistant and tough.
Often, their visitors are well on in years, and it is important to address lighting in parking areas, walkways, and lobbies.
LIGHTING TASKS Many engineers share Kennedy's view that within a decade or two, most current lighting strategies will be as antiquated as the vacuum tube radio.
If you are in the beginning stages of a remodel, call in a lighting designer, suggests Steve Goldmacher, director of corporate communications for Philips Lighting.
Amtech Lighting Services provides a complete range of lighting services, including: Survey, Design, and Installation of Lighting Retrofits; Group Relamping and Lighting Fixture Cleaning; Planned Lighting Management Agreements; Electrical Sign Repairs; Outdoor Lighting Design, Installation, and Maintenance; Electrical Rollout Projects; and Lighting retrofits, with flexible payment options
It's poor lighting they have a problem with, not artificial light itself.
By the time Jean Rosenthal entered, or created, the field during the Great Depression, cost was definitely an object, as it is today, and in some instances, necessity became the mother of invention as stage lighting took the place of elaborate scenery.
CRO estimates that this partnership could potentially result in annual energy savings of 80% for lighting.
Methods of lighting developed that were ample, yet deliberately soft-focused, gently nuanced, and painterly in manner, throwing emphasis onto tonal relations rather than contour.
A three-year landmark building lighting study nearing completion by the International Association of Lighting Management Companies (NALMCO) is expected to provide a roadmap for achieving potential savings of up to 10 percent of the lighting costs of many building owners everywhere for the life of the building - all by simply cleaning fixtures.
Floored by the kaleidoscope of colors, I'm eager to find out how lighting designers create such a spectacular visual display.
Transaction Represents First International Marketing and Distribution Agreement for Lighting Science Group
However, penetrating the general-illumination market, which is dominated by incandescent and fluorescent lighting, will require brighter, white LEDs that can produce the same quality of light as conventional light sources do.
Tom Robbins' company, Turbo Cat Systems in Thousand Oaks, makes mountain-bike lighting systems.