The word when said, may indicate that is going to be a difficult situation, a hard time, or something is, or
will be, happening to them (you or everyone) that is bad (we guess), a bad
day, a bad time or perhaps a stressful situation. This expression is more often said by the
Black, so-called African-American, Negro
race more often than other races, and is sometimes heard as an expression or expressed for some unknown reason to everyone around leaving everyone to wonder what is going wrong in this person's life.
Jack, a homeless Negro man, awakened from his
sleep after a night sleep in a homeless shelter and says to
Toby... "Today is going to be a mother fucker!"
Toby… yep!