Synonyms of unbeknownst

Adjective

1. unbeknown(predicate), unbeknownst(predicate), unknown (vs. known)

usage: (usually used with `to') occurring or existing without the knowledge of; "a crisis unbeknown to me"; "she had been ill for months, unbeknownst to the family"

Adverb

1. unbeknown, unbeknownst

usage: without someone's knowledge; "unbeknownst to me, she made all the arrangements"