—v.t. 1. to release the air or gas from (something inflated, as a balloon): They deflated the tires slightly to allow the truck to drive under the overpass. 2. to depress or reduce (a person or a person's ego, hopes, spirits, etc.); puncture; dash: Her rebuff thoroughly deflated me. 3. to reduce (currency, prices, etc.) from an inflated condition; to affect with deflation.