miller's-thumb [mil′ərz t̸hum′]
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio.
Used by arrangement with John Wiley & Sons, Inc.
The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Any of several small freshwater sculpins of the genus Cottus, especially C. gobio, found in Europe and North America and having a large spiny head and spiny fins.
Origin: From its stocky, thumblike shape (the phrase miller's thumb was originally a folk expression referring to millers who gave short weight by tipping the scales with their thumbs).