The term 'END OF AN ULTIMATUM' can be represented by two crossword solutions: ELSE (4 letters) and ORELSE (6 letters). An ultimatum is a demand or warning that is issued with the intention of forcing a person or group to comply. It usually involves a threat of some kind of action if the demand is not met. The term 'END OF AN ULTIMATUM' implies that the ultimatum has been issued and the recipient must either accept the terms or face the consequences. The two crossword solutions, ELSE and ORELSE, represent this idea of having to accept the ultimatum or ELSE face the consequences.