n. pl. triceps
A large three-headed muscle running along the back of the upper arm and serving to extend the forearm.
[From Latin, three-headed : tri-, tri- + caput, head; see kaput- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.