IPA: /ɪmˈprɒvɪzə/
KK: /ɪmˈprɑɪvɪzər/
A person who creates or performs something spontaneously without preparation, often in music, theater, or other forms of art.
The improviser quickly adapted to the changing situation during the performance.
Improviser → It is formed from "improvisus" (from Latin, meaning not seen beforehand or unexpected) and the suffix "-er" (meaning a person who). An improviser is a person who creates or performs spontaneously without preparation.
Think of someone who creates something 'unexpectedly' ('improvisus') — that's why an improviser is someone who performs without prior planning.