A telltale sign is something that clearly shows what's going on or who's involved. This could be an indicator of guilt, or a giveaway that someone has done something they shouldn't have.
The word "telltale" often refers to a behavior or action that's hard to hide or deny. For example, if you're hiding behind a curtain and then suddenly you accidentally knock it over, your sneaky attempt to stay hidden becomes a telltale sign of what you were trying to do. It's like leaving a trail of breadcrumbs - even if you try to cover them up, someone might still see where you've been. Similarly, if you're a great cook but always eat the leftovers for yourself, that could be a telltale sign of your own taste buds being too involved in the recipe!
How common is "telltale"?
Word telltale is considered rare in modern English. It has a balanced usage among all categories: speech, fiction, newspapers and academic texts.
Definitions
noun
One who divulges private information with intent to hurt others.
An indicator, such as a warning light, that serves to warn of a hazard or problem.
(figuratively) Something that serves to reveal something else.
Example: The telltale was the lipstick on his shirt collar.
(music) A movable piece of ivory, lead, or other material, connected to the bellows of an organ, whose position indicates when the wind is exhausted.
(nautical) A length of yarn or ribbon attached to a sail or shroud etc to indicate the direction of the flow of the air relative to the boat.
(nautical) A mechanical attachment to the steering wheel, which, in the absence of a tiller, shows the position of the helm.
(nautical) A compass in the cabin of a vessel, usually placed where the captain can see it at all hours, and thus inform himself of the vessel's course.
(engineering) A machine or contrivance for indicating or recording something, particularly for keeping a check upon employees (factory hands, watchmen, drivers, etc.) by revealing to their employers what they have done or omitted.
