The act of imagining ones penis going through a meat grinder in order to counter-act the effect of sexual stimulus, therefore reducing an erection.
Often used in public situations when not wanting it to become awkward at the sight of your stiffy.
Person with erected phallus :
'hey Ed i've got such a hard on over Mrs.Mullen, she is such a MILF'
'dude i know! but quick, you'll have to meat grinder it'