Unclench

глагол разжимать Например: to unclench one's fist — разжимать кулак

Большой англо-русский словарь

Unclench

transitive verb 1. to open from a clenched position 2. to release from a grip intransitive verb to become unclasped or relaxed

Энциклопедический словарь Мерриама-Вебстера