is a specific kind of: alter, change, modify.

is a broader term that covers: foul | contaminate, foul, pollute | smear | slime | muddy, muddy up | splash | mire, muck, muck up, mud | crock | blemish, spot.

is the opposite of: clean, make clean.

derivation: dirtying, soiling, soilure | dirt, filth, grease, grime, grunge, soil, stain.