To size up somebody is to look at them and judge what they are like. Size up the opposition, size up the room.
It is done quickly and usually without being noticed, which is what makes it different from studying. It works on situations as well as people, so you can size up a job before taking it.
1phrasesize upTo look at somebody and judge what they are like.
“He took a moment to size up the men at the far table.”
size up is a phrase.
Practised in Ways of Looking