1. Any of numerous small bloodsucking parasitic arachnids of the family Ixodidae, many of which transmit febrile diseases, such as Rocky Mountain spotted fever and Lyme disease.
2. Any of various usually wingless, louselike insects of the family Hippobosciddae that are parasitic on sheep, goats, and other animals.

[Middle English teke, tik, perhaps from Old English *ticca.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.