IPA: /ˈblɒkˌbʌstə/
KK: /ˈblɑkˌbʌstər/
A very popular movie, book, or other entertainment that sells a lot and attracts many people.
The new superhero movie is expected to be a blockbuster this summer.
Blockbuster → It is formed from "block" (from Old English *blocc*, meaning to obstruct or impede) and "buster" (from the verb "bust", meaning to break or burst). The word "blockbuster" originally referred to a bomb that could destroy a block of buildings, and now it describes a highly successful film or event that captures widespread attention.
Think of something that 'obstructs' ('block') and 'breaks' ('buster') through barriers — that's why a blockbuster is something that breaks through to great success.
No commonly confused words.