"Grousing" is Tommy Atkins for grumbling, which is an Englishman's birthright.
No doubt you were often bored, and did your share of grousing.
Grousing because he can't sit in an easy-chair and swig toddies no end!
I suppose he was grousing and grumbling about that when you went out for a walk this afternoon.
After all, Richenda's "grousing" was a little spoiling her fun.