joker

noun

1. 1

   a playing card that is usually printed with a picture of a jester

2. 2

   an inconspicuous clause in a document or bill that affects its meaning in a way that is not immediately apparent

   when I demanded my money he showed me the joker in the contract

3. 3

   a person who enjoys telling or playing jokes

4. 4

   a person who does something thoughtless or annoying

   some joker is blocking the driveway