joker
noun
jok·er
| \ ˈjō-kər
\
\
Definition of joker
1a
: a person given to joking : wag
2
: a playing card added to a pack as a wild card or as the highest-ranking card
3a(1)
: an ambiguous or apparently immaterial clause inserted in a legislative bill to make it inoperative or uncertain in some respect
(2)
: an unsuspected, misleading, or misunderstood clause, phrase, or word in a document that nullifies or greatly alters it
b
: something (such as an expedient or stratagem) held in reserve to gain an end or escape from a predicament
c
: an unsuspected or not readily apparent fact, factor, or condition that thwarts or nullifies a seeming advantage