water key
(redirected from Waterkey)water key
n.
A lever covering a small hole on certain brass instruments that is pressed to drain accumulated fluid, as from condensation of water vapor in the player's breath.
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.