Phrasal Verb: Mess about

Meaning: Not be serious, not use something properly

Example: The children were MESSING ABOUT with the TV remote control and broke it.

Meaning: Treat someone badly

Example: He is always MESSING me ABOUT and never does what he promises.

Meaning: Have a sexual relationship outside marriage or a permanent relationship

Example: He's not faithful- he's been MESSING ABOUT since they were married.