FOUL UP

v. , informal 1. To make dirty. The birds fouled up his newly washed car. 2. To tangle up. He tried to throw a lasso but he got the rope all fouled up. 3. To ruin or spoil by stupid mistakes; botch. He fouled the whole play up by forgetting his part. 4. To make a mistake; to blunder. Blue suit and brown socks! He had fouled up again. 5. To go wrong. Why do some people foul up and become criminals?