informal

1 : to make a mistake : to do something incorrectly

• About halfway into the recipe, I realized that I had messed up, and I had to start over.

— often followed by on

• She’s afraid she’ll mess up on the test.
• I messed up on my first attempt.

2 a mess something up or mess up something : to make mistakes when you are doing or making (something)

2 b mess something up or mess up something : to make (something) dirty or untidy : to make a mess of (something)

• Don’t mess up my room
• The wind messed up her hair.

2 c mess something up or mess up something : to damage or ruin something

• She’s really messed up her life
• His life has been messed up by his drug addiction.

3: to damage or change something so that it does not work properly

• I don’t know what I did, but I somehow messed up the computer.
• My watch has been messed up ever since I dropped it in the sink.
• The mountains messed up the cell phone signal.

4 a mess someone up or mess up someone : to beat and injure someone

• He got messed up by a gang of bullies.
• They messed him up pretty badly.

4 b mess someone up or mess up someone : to make someone very upset and unhappy

• Breaking up with her boyfriend has really messed her up.
• She’s been pretty messed up ever since she broke up with her boyfriend.