That person (colloquial); often with a familiar or slightly derogatory tone — ‘that guy’ or ‘that fellow’.
そいつは本当に嫌な奴だ。
That guy is really unpleasant.
そいつが犯人だとは思えない。
I can't believe that person is the culprit.
そいつ、また遅刻したよ。
That guy was late again.
That (thing); a casual way to refer to an object (like ‘that one’).
その箱の中のそいつを取ってくれ。
Please take that one from inside the box.
このパソコン、古いけどそいつはまだ動くよ。
This computer is old, but that one still works.