needle valve definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a thin, tapered valve that is usually precisely set to control the flow of fluid through a cone-shaped opening: used esp. in carburetors
needle valve definition by American Heritage Dictionary
A valve having a slender point fitting into a conical seat, used to regulate accurately the flow of a liquid or gas.