noun
1. : to make dirty : contaminate
the ranchers used water out of open creek holes that was sometimes alkali and fouled up by stock — Bruce Siberts
2. : to spoil by making mistakes or using poor judgment : confuse
no army would risk fouling up a major landing — Linnell Jones
3. : to have a depressing effect on : darken : lower
a sad sack like that one only fouls up the spirit of the ward — Atlantic
4. : entangle , choke , block
in two or three years the ivy should have been fouling up the television aerial — R.M.Yoder
a big car trying to get into a small parking space fouled up — Bill Hatch
intransitive verb
: to become confused : get into difficulty : bungle
he couldn't shake the feeling that it was his fault. He had fouled up — Pat Frank