adj.未知的,不为人知的;
例句:
He did it unbeknown to us.
他瞒着我们做了那事.
His past is ancient and unbeknown just like his true power.
他的过去古老而不为人知,就如同他的真实力量一般.
He did it unbeknown to me.
他瞒着我干那件事.