Wiktionary
grumping
vb. (present participle of grump English)
Usage examples of "grumping".
The kids go off to school grumping, husband rushes off to work with acid indigestion, and mother feels let down because she has just lost her captive audience.
Not after the visit from the pair of mages, and not with Tellis looking sideways & him and grumping at everything he did, as if he'd suddenly been declared a thief-or worse.