I didn't realise ○○ means that if you use it when talking about a person (またはperson's personality)
I didn't know what ○○ means when you use it to talk about a person
「〇〇が人に使われるとそういう意味になるのは知らなかった」= I didn't realise ○○ means that if you use it when talking about a person (またはperson's personality) / I didn't know what ○○ means when you use it to talk about a person
ボキャブラリー
realise/know = 知る
means = 意味をする、意味になる
use = 使う
when = ~の時、~の場合
talking = 話す事
about = ~について
a person = 人
personality = 性格