a person who heedlessly or maliciously reveals private or confidential matters; tattler; talebearer.

a thing serving to reveal or disclose something.

any of various indicating or registering devices, as a time clock.

Music . a gauge on an organ for indicating the air pressure.

an indicator showing the position of a ship's rudder.

a row of strips hung over a track to warn train crew members on freight trains that a low bridge, tunnel, or the like is approaching.

Yachting . (on a sailboat) a feather, string, or similar device, often attached to the port and starboard shrouds and to the backstay, to indicate the relative direction of the wind.

Squash . a narrow piece of metal across the front wall of a court, parallel to and extending 17 inches (43.2 cm) above the base

a ball striking this is an out.

that reveals or betrays what is not intended to be known

a telltale blush.

giving notice or warning of something, as a mechanical device.

adjective

disclosing , evidential , giveaway , indicatory , informative , meaningful , pointing to , prognostic , significant , significatory , suggestive , busybody , clock , gossip , hint , important , indication , informer , revealing , sign , squealer , suggestion , talebearer , tattler , tattletale

noun

blab , gossiper , gossipmonger , newsmonger , rumormonger , scandalmonger , tabby , talebearer , taleteller , tattle , tattler , tattletale , whisperer