素不相识 [- bù xiānɡ shí]be strangers to each other; be a complete stranger to...; didn't know ... before; have never met [seen] each other before; not to know each other at all; We are not acquainted with each other.; We have never known each other.:
•¶ 我与他素不相识。 I don't know him at all.; He's a perfect stranger to me.