IPA: //ˈmɛɡhɪt//
KK: /ˈmɛɡhɪt/
A very successful product or event, especially in entertainment, like a movie or song that becomes very popular.
The new superhero movie was a megahit, breaking box office records.
Megahit → It is formed from "mega-" (from Greek "megas", meaning great or large) and "hit" (from Old English "hyttan", meaning to strike or achieve). The word "megahit" refers to a very large or great success, particularly in entertainment or music.
Think of something that is 'great' ('mega-') and has 'struck' ('hit') a chord with many people — that's why a megahit is a huge success.