cop out

Short definition from Wiktionary

Verb

1. 1
   To avoid or shirk, either by failing to perform, or by performing in a grossly insufficient, negligent, or superficial manner.
2. 2
   To plead guilty and ask for mercy.
3. 3
   To blame; to assign blame to; to get into trouble.
4. 4
   To remove from a situation or crowd, such as for arrest or punishment.
5. 5
   To leave a gang.
6. 6
   To abandon, let down or betray (someone).
7. 7
   To win (someone) over; to get on (someone's) good side.

Noun

1. 1
   Avoidance or inadequate performance of a task or duty; the action of copping out.
2. 2
   An excuse made in order to avoid performing a task or duty; a reason offered when someone cops out.
3. 3
   A person who cops out.