A colloquial conjunction meaning 'but' or 'however', commonly used in spoken Japanese to soften contrast or introduce a contrasting statement.
行きたいんだけど、今日は予定があるんだ。
I want to go, but I have plans today.
いい考えだけど、費用が高すぎる。
That's a good idea, but the cost is too high.
彼は親切だ。だけど少し不器用だ。
He's kind. However, he's a bit clumsy.