loosen up

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• verb intransitive to become loose; to loosen
• verb colloquial to relax, act less seriously.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb become less tense, less formal, or less restrained, and assume a friendlier manner
• verb make one's body limber or suppler by stretching, as if to prepare for strenuous physical activity
• verb cause to feel relaxed
• verb cause to become unblocked
• verb become less tense, rest, or take one's ease