Phrasal Verb: Mess with

Meaning: Become involved in something damaging or dangerous

Example: He's been MESSING WITH cocaine.

Meaning: Annoy, bother

Example: Don't MESS WITH me or there will be trouble.

Meaning: Associate (negative)

Example: He's been MESSING WITH some dangerous people.

Meaning: Try to repair or improve, usually unsuccessfully

Example: She's been MESSING WITH it for hours and it still doesn't work.