Heenan's Universal Dictionary

A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - XYZ

ULTIMATUM
The last demand before resorting to concessions.   [Ambrose Bierce]

UMFRIEND
Sure sign of an uncertain sexual relationship. "This is my um friend." (see friend, item).  [Palo Alto]

UNINSTALLED
Made redundant; fired.   [Palo Alto]

UNOBTAINIUM
Accessory made from expensive, high-tech material.   [MTBike]

UNKINDNESS

Collective noun for ravens (archaic)

URINE
Opposite of "you're out"   [Rural]