Colloquial contraction of 'to iu ka' used to rephrase, soften, or correct what was just said—like 'or rather' / 'I mean' in English.
彼、優しい、つーか甘いところがあるよね。
He's kind—well, I mean he's kind of soft, isn't he?
明日行ける、つーか行くつもりなんだけど予定がまだ未定で…。
I can go tomorrow—well, I plan to go, but my schedule is still uncertain...
彼女、仕事ができる、つーか頼りになる人だ。
She's capable—rather, she's someone you can rely on.