a dead giveaway

a dead giveaway

A clue, detail, action, etc. that obviously reveals something else. Your shoes are totally sticking out of the blankets! That's a dead giveaway that you're planning on sneaking out as soon as mom says good night to us. The homemade card was a dead giveaway that they had forgotten to buy us a gift.
See also: dead, giveaway

dead giveaway

something that reveals a fact or an intention completely. The car in the driveway was a dead giveaway that someone was at home.
See also: dead, giveaway
References in periodicals archive ?
It wasn't hard to spot Aston, driving around in his souped-up Audi, below - that JLS number plate is a dead giveaway.
But the corpse's cold, stiff hand was a dead giveaway.
Mustaches on single relatives of either sex are a dead giveaway.
Such behavior is a dead giveaway that the visible disk of these galaxies lies embedded in a much larger and more massive halo of unseen material.
The 77-year-old actor's hair may have turned a distinguished shade of silver, but the distinctive eyes are a dead giveaway.