Casual conversation or idle chat without a specific purpose; small talk among friends or before/after meetings.
会議の前に少し雑談してから始めましょう。
Let's have a little small talk before starting the meeting.
彼とは仕事の話より雑談のほうが多い。
I chat more casually with him than I talk about work.
雑談に花が咲いて、会話が止まらなかった。
The small talk became lively and the conversation didn't stop.