from The American Heritage® Dictionary of the English Language, 4th Edition
- transitive v. To loosen from a clenched position; relax: unclench one's fists.
- intransitive v. To become unclenched.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- v. to open (something that was clenched)
- v. to relax, especially one's muscles
from the GNU version of the Collaborative International Dictionary of English
- transitive v. Same as unclinch.
from The Century Dictionary and Cyclopedia
- To open, or to force open, as the closed hand.
From un- + clench. (Wiktionary)