図星 means “to guess correctly”. We usually use this word when one person is able to guess exactly how another person’s feelings or opinions.
If we look at the kanji characters directly, 図星 translates to “the star in the map / diagram” but its original meaning was “the center of the target” or “bullseye.” Much like in English, it was a term often used in archery as the character 図, or “map”, represented the circles of a target and 星, or “star”, represented the center point. So when your opinion or feeling is guessed and revealed by another person, it’s like an arrow shooting and suddenly hitting right in the center of the target. Bullseye!
In Japan, having your feelings revealed is a kind of negative thing. In archery, the idea is that the arrow should hit the weak point of the target - and for Japanese people, our feelings or internal thoughts are viewed as a weak point. Therefore 図星 can’t be used when the person is ok with his or her feelings being revealed or known.
図星 is a noun, and it is often combined with a passive verb to express the embarrassed feeling of the person whose feelings were revealed. So be careful how you use this word around your friends or family!
He guessed exactly what I was thinking, and I felt embarrassed.
You are interested in Mr. Yamada! I’m right, aren’t i?