1.  cliffhanger(n = noun.event) - a contest whose outcome is uncertain up to the very end;
is a kind of competition, contest

2.  cliffhanger(n = noun.communication) - an episode that ends in suspense;
is a kind of episode, installment, instalment

1.  a contest whose outcome is uncertain up to the very end. [WordNet 1.5]

2.  an episode of a drama that ends in suspense. [WordNet 1.5]