GRE TOEFL optimum Definition The most favorable or ideal condition or level. Example "This plant grows at its optimum in moist, shaded soil." Sign in to save GRE Quiz → TOEFL Quiz → ← optimistic option → Study tips featuring "optimum" Write GRE Words Into Your Own Sentences TOEFL Academic Vocabulary: Study by Topic Related words GRE swill GRE taper GRE testy GRE abacus SAT abase GRE abash GRE abate GRE abbreviate GRE abbreviation SAT abdicate SAT abdomen GRE abduct