noun, verb (used with or without object) Slang.
Origin of ump
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
short for umpire (n.), by 1915, American English.
Online Etymology Dictionary, © 2010 Douglas Harper
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.