Meaning of the word "on cloud nine" in English

What does "on cloud nine" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

on cloud nine

US /ɑn klaʊd naɪn/
UK /ɒn klaʊd naɪn/

Idiom

extremely happy; ecstatic

Example:
After winning the lottery, she was on cloud nine.
He's been on cloud nine ever since he got the promotion.