Green’s Dictionary of Slang

read n.

[read v. (1a)]

a sense of understanding, assessment.

[Can](con. 1920s) O.D. Brooks Legs 61: He started firing questions. I knew he was trying to get a read on me.
[US]W.D. Myers Sunrise Over Fallujah 246: ‘My read is that it [i.e. a firefight] won’t be necessary’.