Caught short is an idiomatic expression that describes being unexpectedly or suddenly in a situation of lacking something that one needs. Antonyms for this phrase would include being prepared, having enough, being well-provisioned or having plenty. One might use these words to describe a comfortable situation where all needs are met, or a state of being in which one is not lacking anything. For example, "Prepared travelers seldom find themselves caught short without enough water or food during their journeys." Another way to express an antonym for caught short might be to say "well-stocked" or "well-equipped" to describe being fully prepared and anticipating all possible needs.