K (k): a thousand.
"I could retire with 100 K (k)!"
kick back: relax and enjoy.
"I wish I could kick back at the beach today."
kick off: die.
"My dog finally kicked off."
killer: something exceptional or great.
"Wow, your boyfriend is killer!"
knock: condemn.
"Don't knock it unless you've tried it."
knockout: beautiful woman; handsome man.
"Benjamin is already a knockout!"
kook: peculiar person.
"Stop acting like a kook!"