renege

Concise Oxford English Dictionary © 2008 Oxford University Press:
renege /rɪˈneɪg, rɪˈniːg/

▶verb

• 1 go back on a promise, undertaking, or contract.

  ■ archaic renounce or abandon.

• 2 another term for revoke (sense 2).

– derivatives
reneger noun.

– origin C16: from med. L. renegare, from L. re- (expressing intensive force) + negare ‘deny’.