Definition of: ultimatum

(ul′tə·mā′təm, -mä′-) noun plural ·tums or ·ta (-tə)
1. A final statement, as concerning terms or conditions; in diplomacy, the final terms offered by one party, as during negotiations concerning a treaty, the rejection of which by the other party will result in breaking off all negotiation; loosely, a last proposal, offer, concession, or demand.
2. Anything ultimate. [<NL <LL, neut. of ultimatus. See ULTIMATE.]