IPA: //ʌn.rɪˈstreɪnd//
KK: /ʌnˈrɛstreɪnd/
Not limited or controlled; acting freely and without restrictions.
The children played with unrestrained joy in the park.
Comparative: more unrestrained
Superlative: most unrestrained
Unrestrained → It is formed from "un-" (meaning not) and "restrain" (from Latin "restringere", meaning to bind back). The word "unrestrained" means not bound back or free from limitations.
Think of 'not' ('un-') being applied to 'binding back' ('restringere') — that's why unrestrained means free and without limits.