IPA: //ʌnˈsʌsɛs//
KK: /ʌnˈsʌsɛs/
The state of not achieving a desired goal or outcome.
His attempt to start a business ended in unsuccess, leaving him disappointed.
Unsuccessful → It is formed from "un-" (meaning not) and "success" (from Latin "successus", meaning outcome or result). The word "unsuccessful" means not achieving a desired outcome or result.
Think of 'not' ('un-') achieving a 'result' ('success') — that's why unsuccessful means failing to achieve what you wanted.