befoul, defile, maculate
contaminate, pollute
back up, choke, choke off, clog, clog up, congest
afoul, fouled
filthy, nasty
cruddy, filthy, nasty, smutty
cheating, dirty, unsporting, unsportsmanlike
fetid, foetid, foul-smelling, funky, ill-scented, noisome, smelly, stinking
dirty, marked-up
disgustful, disgusting, distasteful, loathly, loathsome, repellant, repellent, repelling, revolting, skanky, wicked, yucky