Meaning of the word unbeknownst in English

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

unbeknownst

US /ˌʌn.bɪˈnoʊnst/
UK /ˌʌn.bɪˈnəʊnst/

Adverb

without the knowledge of (someone)

Example:
Unbeknownst to her, he had already made plans to surprise her.
The decision was made unbeknownst to the rest of the team.