adjective, strop·pi·er, strop·pi·est. British Informal.
bad-tempered or hostile; quick to take offense.
Origin of stroppy
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
adjective -pier or -piest
British informal angry or awkward
Word Origin for stroppy
C20: changed and shortened from obstreperous
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
1951, perhaps a slang mangling of obstreperous.
Online Etymology Dictionary, © 2010 Douglas Harper