unbeknownun‧be‧known /ˌʌnbɪˈnəʊn $ -ˈnoʊn/ (also un‧be‧knownst /-ˈnəʊnst $ -ˈnoʊnst/ written) adverb [sentence adverb] 
Examples
Unbeknown to him, his wife had been trying to phone him all morning.
ExamplesEXAMPLES FROM THE CORPUS
Thesaurus- But unbeknown to Ivor, Stroud had no intention of parting with the money.
- Thus unbeknown to the competitors, the last valid part of the competition was removed four days before the submission date.
- Under the old system many women amass secret savings unbeknown to their husbands.
- You've crept back unbeknown to me.
Longman Language Activatorto not realize what is happening► not know/not realize/have no idea
Phrases · "It's my birthday today." "Oh, I didn't realize. I should have bought you a card."not know/not realize/have no idea (that) · I wish I'd brought my coat. I didn't know it would be so cold.· We didn't realize that he had quit, until he didn't show up at work that day.not know/not realize/have no idea what/how/where etc · My wife and I had no idea how much we would depend upon Social Security in the future.
► be unaware/not be aware formal to not know about a situation or about something that is happening, especially when you should know about it: be unaware/not be aware of: · The child was clearly unaware of the danger.· If any bad feelings existed between the two of them, I was not aware of it.be unaware/not be aware that: · His parents weren't even aware that he smoked.
► have no knowledge of formal to know nothing about a subject or situation because you have not experienced it, read about it, or heard about it: · The general public has little or no knowledge of what is happening inside prisons.· The State Department said it had no knowledge of any threats to U.S. security.
► unbeknown to somebody also unbeknownst to somebody use this about something that was happening without you knowing about it at the time: · Unbeknown to me, Denise had her own plan.· Unbeknownst to the public, he was involved in covering up the scandal that was to rock the nation.
► little did I/she/he etc know use this when you did not know or imagine that something was true or would happen: little did I/she/he etc know that: · Little did she know that this picture would one day be worth more than a million dollars.· Little did I know then that I would be working in Los Angeles 35 years later.
► for all I/you/they etc know spoken say this when you know almost nothing about a situation and to suggest something that might have happened or be true, especially something unlikely: · They may have gone to South America, for all we know.· You shouldn't have accepted a ride from him. For all you knew he might have been a mass murderer.
► be unconscious of if you are unconscious of the effect of something that you have said or done, you do not realize how it affects other people: · She appeared to be unconscious of the amusement she had caused by her remarks.· Like many tourists they were unconscious of the fact that they had deeply offended their hosts.
► oblivious someone who is oblivious to what is happening around them does not notice it and continues to do other things without being affected by it: oblivious of: · They soon fell asleep, oblivious of the danger.oblivious to: · The walkers in front crossed the ledge easily, seemingly oblivious to the fact that there was a 3000 foot drop on either side.· In the sitcom she plays a New York executive who's totally oblivious to the feelings of others.
PHRASES FROM THE ENTRY► unbeknown to somebody
unbeknown to somebody without that person knowing about it: - Unbeknown to me, Denise had her own plan.
- Unbeknownst to the public, he was involved in covering up the scandal that was to rock the nation.
Unbeknown to him, his wife had been trying to phone him all morning.