1. A final demand or statement of terms, the rejection of which will result in retaliation or termination of relations
The government issued an ultimatum to the rebels.
O governo emitiu um ultimato aos rebeldes.
2. A final warning or threat made as a condition for further negotiation
She gave him an ultimatum: stop drinking or she would leave.
Ela deu um ultimato a ele: parar de beber ou ela o deixaria.