Grumpy vs Grum - What's the difference?

As adjectives the difference between grumpy and grum

is that grumpy is unhappy, dissatisfied and/or irritable while grum is morose, stern, surly, sullen.

(er)

Unhappy, dissatisfied and/or irritable.

Tommy feels grumpy today because his friend stole his ball.

Michael Finnell was grumpy''', but became even '''grumpier when the Celtics lost.

* grouchy * surly * truculent

(grummer)

Morose, stern, surly, sullen.

* 1891 , Mary Noailles Murfree, In the "Stranger Poeple's" Country , Nebraska 2005, p. 58:

She cast a speculative look upon her husband, silent and grum as if he had been thus gruffly carved out of wood.

Low, deep in the throat; guttural

a grum voice

* glum * grim * sour

* grumly * grumness ----