noun

• (US, slang) An attempt, a chance, a turn, a go, originally an attempt to beat someone or something.
  "C'mon. Take a whack at it."
• (originally UK cant, somewhat dated) A share, a portion, especially a full share or large portion.
  "I don’t care about much wine afterwards—I take my whack at dinner—I mean my share, you know; and when I have had as much as I want I toddle up to tea."
• (obsolete) A whack-up: a division of an amount into separate whacks, a divvying up.
• (US, obsolete) A deal, an agreement.
  ""I'll stay if you will." "Good—that's a whack.""

verb

• (slang) To assassinate, bump off.
  "Niko Bellic: So you want me to talk to him? / Jimmy Pegorino: I want you to whack him! And after that I want you to kill all the other rats I surround myself with..."
• (transitive, slang) To share or parcel out (often with up).
  "to whack the spoils of a robbery"
• (sports) To beat convincingly; to thrash.
  "The fidgety Majors were whacked 9-1 by the Kitchener Panthers at Couch and now trail their rivals 2-0 in an increasingly uncomfortable best-of-seven Intercounty Baseball League first-round series."
• (UK, chiefly in the negative) To surpass; to better.
  "Recently I was over in Ireland, I love the place, proper fishing, can't whack it!"