ticktack

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A steady ticking sound, as of a clock.
• noun A prankster's device for tapping on a door or window from a distance.

from The Century Dictionary.

• noun A pulsating sound like that made by a clock or watch; a ticking.
• noun Specifically, the sound of the beating of the heart.
• noun A device employed in playing certain practical jokes, consisting of a small weight so fastened that one at a distance can, by pulling a string, cause the weight to tap against the house or window.
• noun A complicated kind of backgammon, played both with men and with pegs. Compare trick-track, and see the third quotation below.
• With a sound resembling the beating of a watch.

from the GNU version of the Collaborative International Dictionary of English.

• noun A noise like that made by a clock or a watch.
• noun A kind of backgammon played both with men and pegs; tricktrack.
• adverb With a ticking noise, like that of a watch.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• interjection Dated form of tick tock.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun system of signalling by hand signs used by bookmakers at racetracks
• verb make a sound like a clock or a timer