Dictionary.com
Thesaurus.com
Synonyms

up a tree

Idioms  
  1. In a difficult situation, as in They found the drugs in his suitcase, so he was up a tree. This expression alludes to an animal, such as a raccoon or squirrel, that climbs a tree for refuge from attackers, which then surround the tree so it cannot come down. [Colloquial; early 1800s]