IPA: /ˌʌn.rɪˈstreɪnd.li/
KK: /ʌnˈrɛstreɪndli/
In a way that is not controlled or limited; freely and without restraint.
She laughed unrestrainedly at the joke, not caring who was watching.
Unrestrainedly → It is formed from "un-" (meaning not), "restrained" (from Latin "restringere", meaning to bind back or hold back), and "-ly" (meaning in a manner). The word "unrestrainedly" means in a manner that is not held back or limited.
Think of 'not' ('un-') holding back ('restrained') — that's why unrestrainedly means acting without limits.