ad-lib

verb
1
to say something in a speech or a performance that you have not prepared or practised
بداهه گفتن, سخن بداهه گفتن, به صورت فی‌البداهه گفتن
synonym improvise
adjective
1
an ad-lib speech or performance has not been prepared or practised
بداهه, فی‌البداهه