Definify.com
Webster 1913 Edition
Untighten
Un-tight′en
,Verb.
T.
[1st pref.
un-
+ tighten
.] To make less tight or tense; to loosen.
Definition 2024
untighten
untighten
English
Verb
untighten (third-person singular simple present untightens, present participle untightening, simple past and past participle untightened)