warn against

warn against (something)

To caution (someone) not to do something that is dangerous or risky. A noun or pronoun can be used between "warn" and "against." My mother always warned me against hanging out with hoodlums like you, and now I know why. Doctors are warning against spending too much time outside during this week's heatwave.
See also: warn
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

warn someone against someone or something

to advise someone against someone, something, or doing something. We warned them all against going to the region at this time. I warned her against Gerald.
See also: warn
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.

warn against

To advise someone that something is dangerous or problematic and should be avoided: I warned them against driving without seatbelts. The doctor warns against smoking.
See also: warn
The American Heritage® Dictionary of Phrasal Verbs. Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
See also:
References in periodicals archive ?
A GAY American has officially complained to Poland after its president used images of him and his partner in a national speech to warn against homosexual marriage.
Moscow (ENI) -- A Russian organization with close ties to the Kremlin is quoting the Bible, the Jewish Torah and a saying attributed to the prophet Muhammad in an anti-corruption drive to warn against the evils of bribery.
Stanley Hall, a psychologist, warn against teaching about homosexuality.
Chapters claim that starches, not fat, are what fuel heart disease; warn against the health risks of a vegetarian lifestyle (vitamin B12 deficiency is a problem that can only be remedied with supplements, and other important nutrients are much less likely to be consumed in a vegetarian lifestyle); and recommend interval-exercise and weight training for improved heart health rather than long-duration cardiovascular exercise.
The comedian, who features in a series of credit card advertisements that warn against throwing personal details in the bin, said he was embarrassed by his oversight.
The comedian, who stars in advertisements for credit card company Capital One that warn against throwing personal details in the bin, said he was embarrassed by his oversight.
Chapters address the challenges of striving for innovation, warn against the impracticality of "inside-the-box" advertisement, the importance of distinctive advertising (far more so than having a distinctive product!), and much more.
The revised guidelines warn against combining atazanavir + indinavir (possible worse hyperbilirubinemia), and FTC + 3TC (similar resistance profile, without additional benefit).
Two set points for high and low temperature limits energize large alarm lights to warn against out of bounds conditions.
In The Internet Bubble (HarperCollins), Anthony and Michael Perkins, founders of high-tech magazine Red Herring, warn against the euphoria and greed that characterizes the most dynamic and attractive industry of the moment, the frantic business of Internet startups.
Yet researchers uniformly warn against unbridled optimism.
Bright yellow placards warn against eating fish from the bay every day, and against pregnant women eating them at all.
Police have also warn against creating a commotion through loudspeakers or sound equipment.
Global Banking News-November 6, 2014--UK banks warn against splitting branch networks
"We warn against ignoring the Sunni majority and the parliament majority," the leaders said in a statement.