From Longman Dictionary of Contemporary Englishloosen up phrasal verb1 RELAXEDto 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 DSif your muscles loosen up, or if something loosens them up, they stop feeling stiffloosen something ↔ up A massage will loosen up your joints. → loosen→ See Verb table
Examples from the Corpus
loosen up• At first, I just started drinking at parties, to help loosen me up.• Uncle Billy was a great preacher -- he sure could loosen a crowd up.• Hey, loosen up! It's not worth getting upset about something she said.• Our drama teacher would do crazy things, just to get us to loosen up some. 