From Longman Dictionary of Contemporary Englishloosen up phrasal verb1RELAXEDto stop worrying and become more relaxed, or to make someone do thisShe loosened up after she’d had a drink.loosen somebody ↔ upHis welcoming smile helped loosen her up.2DSif your musclesloosen up, or if something loosens them up, they stop feeling stiffloosen something ↔ upA 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.• UncleBilly 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 dramateacher would do crazy things, just to get us to loosen up some.