Misspelling of knapsack.

(military, slang, vulgar) A sleeping bag (especially a heavily-insulated bag).

plural of bollock sack

(slang, vulgar, UK) The scrotum.

(derogatory) Somebody who barely qualifies as human.

plural of gunny sack

(transitive) To put (something) in a sack. / (slang, vulgar, intransitive) To force oneself to become more manly; to toughen up or man up.

Alternative form of towsack

(US) A packed lunch.

plural of sack lunch