n.
A legendary sea creature having the head and upper body of a woman and the tail of a fish.
[Middle English : mere, sea, lake; see mere2 + maid, maid; see maid.]
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.