unbeknownst
adj. C1 Advanced US //ənbiˈnoʊnst// UK //ʌnbɪnˈəʊnst// un·be·knownst
adj. something that happens without someone knowing about it. You use this to describe a secret or a hidden fact that someone is not aware of.
adj. something that occurs or exists without the knowledge of a specific person. Typically used in the prepositional phrase 'unbeknownst to' followed by a noun phrase.
Unbeknownst to the team, the game was cancelled.
Unbeknownst to the local residents, the city council had already approved the new development project.
Unbeknownst to the protagonist, the seemingly minor decision to take a different route home would set in motion a series of events that would change his life forever.
Variant of unbeknown with excrescent -st.