Green’s Dictionary of Slang

puma phr.

[panties up my arse]

a phr. used when one has one’s underwear caught between the buttocks.

[UK]Indep. Rev. 11 June 4: American youth may use the word ‘puma’ as shorthand for ‘comeback’, over here it’s an acronym (Panties Up My Arse) for traumatic underwear.