dead giveaway

plural dead giveaways

1. idiomaticA giveaway that is especially obvious, especially ruinous, or both, disclosing, usually unintentionally, a fact or an intention.

   That disguise is a dead giveaway! Choose something less obvious.

   2 more examples

   "Instead of slowing down his arm when he throws it — a dead giveaway to hitters — Igawa had better arm action, Eiland said"

   2008 March 5, New York Times

   Most torpedoes solved this problem by supplying the engine with compressed air, but this held a couple of problems, as regular air is only 21% oxygen, meaning that 79% of said compressed air is useless and will simply be vented as a hot gas, along with any combustion products from the burning of the fuel. This would then lead to a train of bubbles that were something of a dead giveaway of a torpedo's presence, and the limited amount of oxygen within the compressed air also limited the torpedo's range. More oxygen would mean fewer bubbles, as there was less exhaust gas; more burn time, as there was more oxygen to burn with the fuel; and a more complete and energetic combustion of the fuel, all of which would allow a torpedo that was equipped with an enriched-oxygen mix to travel further, faster, and stealthier.

   2021 January 20, Drachinifel, 3:24 from the start, in Type 93 Long Lance Torpedo - Long Range Hole Poking Device, archived from the original on 01 Nov 2022