1. (adj)unbeknown(p), unbeknownst(p) (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"
2. (adverb)unbeknown, unbeknownst without someone's knowledge "unbeknownst to me, she made all the arrangements"
Definition of 'unbeknown'
