Acquaintance
noun
You've probably seen the words 知る and 合う by now. This is someone you "know" because you have "come together" before, but that's pretty much it. You don't really know them well, you just met them a couple times so you know who they are. This person is an acquaintance.
しりあい
The readings are that of 知る and 合う. So long as you know those words, you should be able to read this one too.
お知り合いですか?
Do you know each other?
知り合いだから、ちょっと聞いてみるよ。
Since I know that person, I'll ask them about it.
アイツと知り合いだとはゼッタイにバレたくない。
I absolutely don't want it to be known that I'm acquainted with them.