1. (verb)decompress, uncompress restore to its uncompressed form "decompress data"
2. (verb)depressurize, depressurise, decompress decrease the pressure of "depressurize the cabin in the air plane"
3. (verb)relax, loosen up, unbend, unwind, decompress, slow down become less tense, rest, or take one's ease "He relaxed in the hot tub"; "Let's all relax after a hard day's work"