Tell-tale

n. 1. One who officiously communicates information of the private concerns of individuals; one who tells that which prudence should suppress.

2. (Mus.) A movable piece of ivory, lead, or other material, attached to an organ, that gives notice, by its position, when the wind is exhausted.
3. (Naut.) (a.) An instrument which, by communicating with a small barrel on the axis of the steering-wheel, indicates the position or situation of the helm. (b.) A compass in the cabin of a vessel giving information to persons below of the course of the vessel. Totten.
4. (Mach.) A machine or contrivance for indicating or recording something, particularly for keeping a check upon employés, as factory-hands, watchmen, drivers, check-takers, and the like, by revealing to their employers what they have done or omitted.