loosen up (Verb) — Cause to become unblocked. ex. "The medicine loosened up my nose in minutes!"
loosen up (Verb) — Become less tense, less formal, or less restrained, and assume a friendlier manner. ex. "our new colleague loosened up when he saw that we were a friendly group"
loosen up (Verb) — Make one's body limber or suppler by stretching, as if to prepare for strenuous physical activity.
loosen up (Verb) — Become less tense, rest, or take one's ease. ex. "He loosened up in the hot tub"
loosen up (Verb) — Cause to feel relaxed.