loosen up phrasal verb ( see also ↑ loosen )
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.