The act of fiddling with, meddling in, or teasing something/someone; tinkering or playful meddling.
彼は会話中も髪のいじりが止まらない。
He can't stop fiddling with his hair even during conversations.
スマホいじりで授業に集中できない学生が増えている。
More students can't concentrate in class because they play with their smartphones.
彼のいじりが度を越して、不快に感じた。
His teasing went too far and felt unpleasant.