pocket veto

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The indirect veto of a bill received by the President within ten days of the adjournment of Congress, effected by retaining the bill unsigned until Congress adjourns.
2. n. A similar action exercised by a state governor or other chief executive.

Wiktionary

1. n. US A (de facto) veto of a bill by the US President by restricting Congressional action on the bill, as, figuratively, by carrying the bill in his pocket until the deadline for signing it has passed.

GNU Webster's 1913

1. The retention by the President of the United States of a bill unsigned so that it does not become a law, in virtue of the following constitutional provision (Const. Art. I., sec. 7, cl. 2): “If any bill shall not be returned by the President within ten days (Sundays excepted) after it shall have been presented to him, the same shall be a law, in like manner as if he had signed it, unless the Congress by their adjournment prevent its return, in which case it shall not be a law.” Also, an analogous retention of a bill by a State governor.

WordNet 3.0

1. n. indirect veto of legislation by refusing to sign it