n. This expression is rooted in Confederate America when cruel and unusual punishment was a common thing. The porch sucker, much like a cotton picker, was a deliquent servant. This bottom feeder was sentenced to sucking the plantation porch clean on hands and knees until thy had served their time.
In modern times the porch sucker is some crazy ass fool who has neglected his/her duties as a friend, or stood you up to hook up with the opposite sex.
v. You can also say "this sucks a porch!". This implys a great distaste for some form of delinquency or inadequacy.
"I can't believe you ditched me to suck her porch"
"God, my stupid porch sucking friends are so unreliable!"
"@#?!!@! PORCH SUCKER!!@@#@!?!"