[know-it-all] {n.} A person who acts as if he knows all […]

[knowledge] See: [A LITTLE KNOWLEDGE IS A DANGEROUS THING], [TO THE […]

[knuckle] See: [BUCKLE DOWN] or [KNUCKLE DOWN], [RAP ONE'S KNUCKLES].

[knuckle down] See: [BUCKLE DOWN].

[knuckle under] {v. phr.} To do something because you are forced […]

[KO] A common misspelling of ok.

[KOL] "Kiss on lips"

Where there are no tigers, a wild cat is very self-important.

[KOS] "Kill on Sight"; used to designate enemies in online games […]

[KREE!] "Attention!"