From Longman Dictionary of Contemporary English loosen up phrasal verb 1 to stop worrying and become more relaxed, or to make someone do this She loosened up after she’d had a drink. loosen somebody ↔ up His welcoming smile helped loosen her up. 2 if your muscles loosen up, or if something loosens them up, they stop feeling stiff loosen something ↔ up A massage will loosen up your joints. → loosen → See Verb table Examples from...