Definition
To have absolutely no acquaintance with someone; to have never met them and know nothing about them.
完全不認識
I ran into him on the street yesterday, but I don't know him from Adam.
我昨天在街上遇到他，但我完全不認識他。
She asked me for help, but I don't know her from Adam, so I don't know what she wants.
她向我求助，但我完全不認識她，所以不知道她想要什麼。
The company's boss changed recently, and I don't know the new one from Adam.
公司最近換了老闆，我完全不認識新來的這位。