cop-out

1. A failure to fulfill a commitment or responsibility or to face a difficulty squarely.
2. A person who fails to fulfill a commitment or responsibility.
3. An excuse for inaction or evasion.

Back out of a responsibility or commitment; also, take the easy way out. For example, Don't count on him; he's been known to fake illness and cop out, or She'll cop out and let her assistant do all the work. These meanings are derived from the underworld slang use of cop out for backing down or surrendering. [Late 1950s]

Definition: abandon, quit
Antonyms: be ready, face, ready, take on

The verb has one meaning:

Meaning #1: choose not to do something
  Synonym: opt out