tell·tale 
(tĕltāl′)
(tĕltāl′)n.
1. One who informs on another; a talebearer.
2. Something that indicates or reveals information; a sign.
3. Any of various devices that indicate or register information, especially:
a. A time clock.
b. Nautical A length of yarn or ribbon attached to a shroud, stay, or sail of a sailboat, as to indicate the direction of the wind or the strength of the flow of air over the sail.
c. A row of strips hung above a railroad track to warn a passing train of low clearance ahead.
4. Sports A resonant metal strip, 24 or 30 inches (61 or 76 centimeters) high, across the bottom of the front wall of a racquets or squash court above which the ball must be hit.