To express the anger you feel in words.
Foul Facts was created in 2001.
This Night's Foul Work was created in 2006.
The Foul King was created on 2000-02-04.
Super Foul Egg was created in 1995.
Foul Play Suspected was created in 1935.
Lord Foul's Bane was created in 1977.
By Fair Means or Foul was created in 1988.
Personal Foul - book - was created in 2009-12.
Murder Most Foul was created in 1964-09.
Clean Hands Go Foul was created on 2009-05-26.
It typically refers to someone who is using foul language. The foul language being the 'colorfull words'.
"Foul Play" by Janet Evanovich and Dorien Kelly was first published on July 12, 2008.