Definition of "cilium" [cil•i•um]

• A microscopic hairlike process extending from the surface of a cell or unicellular organism. Capable of rhythmical motion, it acts in unison with other such structures to bring about the movement of the cell or of the surrounding medium. (noun)
• An eyelash. (noun)
• Botany One of the hairs along the margin or edge of a structure, such as a leaf, usually forming a fringe. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Unlike the tower of Iacocca Hall, the cilium is a dynamic structure, in which many of its protein parts are actively altered in response to changing internal and external conditions."
• "The cilium is an elegant molecular machine that powers the swimming of cells as diverse as sperm and pond algae."
• "Many proteins of the eukaryotic flagellum also called a cilium or undulipodium are known to be dispensable, because functional swimming flagella that lack these proteins are known to exist."