Unlace
/ʌnˈleɪs/
Definition 1 of 1
Pro Tip 1/3Physical Action
Used to describe the manual action of loosening threads or strings by pulling. 
She had to unlace the ribbon to open the gift.
Pro Tip 2/3Casual Context
'Unlace' is informal, often used casually in everyday conversations. 
After the match, he sat down to unlace his sneakers.
Pro Tip 3/3Figurative Use
Sometimes used metaphorically to mean 'to relax or lessen tension'. 
The comedian's joke helped to unlace the tension in the room.