A bundle of microtubules and associated proteins that makes up the core of a cilium or flagellum, consisting of nine pairs of microtubules arranged around two single microtubules.
[Greek axōn, axis + Greek nēma, thread; see (s)nē- 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.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.