chief·tain (ch?f?t?n)n. The leader or head of a group, especially of a clan or tribe.[Middle English cheftain, from Old French chevetain, from Late Latin capit?neus, from Latin caput, head; see kaput- in Indo-European roots.]chief?tain·cy n.chief?tain·ship? n.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.