mess around

US /mes əˈraʊnd/
UK /mes əˈraʊnd/
"mess around" picture
1.

ふざける, 遊ぶ

to behave in a silly or playful way

:
Stop messing around and get your work done.
ふざけるのはやめて、仕事を終わらせなさい。
The kids were messing around in the backyard.
子供たちは裏庭でふざけていた
2.

関係を持つ, 浮気する

to have a casual sexual relationship with someone

:
He's been messing around with someone from work.
彼は職場の誰かと関係を持っている
I heard they were messing around for a while before they got serious.
彼らが真剣になる前に、しばらく関係を持っていたと聞いた。