C2to cause or allow something to continue for a period of time: The economy looks set to sustain its growth into next year.He seems to find it difficult to sustain relationships with women.USThe judge sustained (= accepted) the lawyer's objection.Preserving and savingDefending and protectingC2to keep alive: The soil in this part of the world is not rich enough to sustain a large population.Preserving and savingDefending and protecting