loosen up in WordNet English dictionary

1. become less tense, rest, or take one's ease
   "He relaxed in the hot tub"; "Let's all relax after a hard day's work"
   relax  loosen up  unbend  unwind  decompress  slow down 
   
2. make one's body limber or suppler by stretching, as if to prepare for strenuous physical activity
   limber up  warm up  loosen up 
   
3. cause to feel relaxed
   "A hot bath always relaxes me"
   relax  unstrain  unlax  loosen up  unwind  make relaxed 
   
4. cause to become unblocked
   "The medicine unstuffed my nose in minutes!"
   unstuff  loosen up 
   
5. become less tense, less formal, or less restrained, and assume a friendlier manner
   "our new colleague relaxed when he saw that we were a friendly group"
   relax  loosen up