IPA: //ʌnˈprɒmptɪd//
KK: /ʌnˈprɑmptɪd/
Describing something that occurs without being asked or encouraged.
She gave an unprompted compliment about his work.
Unprompted → It is formed from "un-" (meaning not) and "prompted" (from Latin "promptus", meaning brought forth or ready). The word "unprompted" means not brought forth or not initiated by an external cue or stimulus.
Think of 'not' ('un-') being involved in something that is 'brought forth' ('promptus') — that's why unprompted means something that happens without any external prompting.