jok ‧ er /ˈdʒəʊkə $ ˈdʒoʊkər/ BrE AmE noun [countable]
[ Word Family: noun : ↑ joke , ↑ joker , ↑ jokiness , ↑ jocularity ; adverb : ↑ jokingly , ↑ jokily , ↑ jocularly ; adjective : ↑ jokey , ↑ jocular ; verb : ↑ joke ]
1 . informal someone who behaves in a way you think is stupid:
Look at that joker – he’s doing 25 miles an hour at the most.
2 . a ↑ playing card that has no fixed value and is only used in some card games
3 . someone who makes a lot of jokes
4 . the joker in the pack something or someone whose effect on future events cannot be known