1Attributive Originally: designating a fitting designed by Oscar Zerk to allow lubrication to be applied directly to bearings or other moving parts of a machine, consisting of a small tapered nipple against which the nozzle of a grease gun is held by the pressure of the lubricant as it is administered. In later use: designating any fitting designed for this purpose.
2A zerk fitting.
1920s; earliest use found in The Marion Daily Star. From the name of Oscar V. Zerk, Austrian-born U.S. inventor.