fly by

1. To pass (someone or something) by flying. Ethel screamed as a bird flew right by her head and startled her. We all looked up to watch the helicopter flying by. Don't panic, it's just a bumblebee flying by.

2. To pass or go by swiftly, as a of period of time. I don't know, we just started chatting, and then I looked up and two hours had flown by! With the way senior year is flying by, we'll be graduates before you know it! I know the days are long when you have kids this young, but trust me—the years fly by.

3. To pass (someone or something) at great speed. I needed to ask Tom a question, but he flew by my desk before I could get his attention. Police cars flew by, their sirens blaring. Some fool kid flew by on a bike and nearly crashed into a woman walking ahead of me.

4. To make a short, surprise visit. Oh, Paulina only flew by for a few hours, that's why you didn't see her. Hey, when did you fly by the house? I see you left me a note. Aunt Louise gets into town today, so she'll probably fly by on her way to the hotel.

flyby

A flight that travels very close to an intended target, often in outer space. When used as a noun, the phrase is usually written as one word. We'll do a flyby to collect more information on that planet. That pilot was incredibly reckless to do in a flyby in such a populated area! Ever since I was a boy, my dream was to do a flyby of the moon. That's why I became an astronaut.

fly by

1. Lit. to soar past, flying. Three jet fighters flew by. A huge hawk flew by, frightening all the smaller birds.

2. Fig. [for time] to go quickly. The hours just flew by, because we were having fun. Time flew by so fast that it was dark before we knew it.

fly by

1. To pass quickly, as of a moving object or an interval of time: The summer months flew by, leaving us only a few days warm enough for swimming.

2. To visit briefly, often unexpectedly: Some of my old school friends flew by for a short visit last week.

3. To move past in flight: Several geese flew by as we climbed the hill.