unprompt
/ˈʌnprɒmpt/Definitions
1. adjective
Not requiring or given prior warning or notice; sudden
“The unprompted arrival of the guests caught everyone off guard.”
2. verb
To speak or act without being prompted or provoked
“The politician unprompted the crowd with a passionate speech.”
3. noun
A response or action that is not prompted or provoked
“The unprompted applause was a surprise to the performers.”