joker

noun

• A person who makes jokes.
• A funny person.
• A jester.
• A playing card that features a picture of a joker (that is, a jester) and that may be used as a wild card in some card games.
• An unspecified, vaguely disreputable person.

  "Some joker keeps throwing eggs at my windows."

• A man.
• A clause in a contract that undermines its apparent provisions.