Definition of: telltale

(tel′tāl′) adjective
1. Tattling; talebearing.
2. Betraying.
—noun
1. One who improperly gives information concerning the private affairs of others; a tattler.
2. That which conveys information, especially in an involuntary way; a token.
3. An instrument or device, usually automatic, for giving information as to number, position, condition, etc.
4. A row of dangling straps or ropes suspended above a railway track to warn anyone standing on a car roof of the approach of a low overhead structure.
5. A clock to record the times of coming and going, as of workmen, or as a watchman's clock.
6. An index showing the position of a vessel's helm.
7. A yellowlegs or tattler.