To complain somewhat pointlessly. Grumbling usually consists of merely bemoaning an unfortunate/unfair situation instead of attempting to come up with a solution.

A cryptocurrency of little to no value, usually a late-comer to the Bitcoin craze, a copycat cryptocurrency.

A contracted form of the Cockney rhyming slang 'grumble and grunt'. I refers in an unsavoury way to an eligible female.

You may not like it but it's out there as part of our urban linguistic culture.
Certainly in use in the 1960's

Pornographic materials such as magazines, internet sites or videos

A group of pugs (originate from China, large toy breed) containing three or more breed of the dog.

Hunched over, kleenex in one hand, cock in the other. Adopting a similar position to a grumbling old man

noun:

1) One who prematurely denies a correct response only to come full circle and carefully explain the same answer
2) One who is easily mistakable for a person of a lesser education level
3) One who may become moist at the sound of the Orphan Whisperer's voice