Mux \Mux\, n. [Cf. Mixen.] Dirt; filth; muck. [Prov. Eng.] --ose.
Source: Webster's Revised Unabridged Dictionary (1913)
Mux \Mux\, v. t. To mix in an unitidy and offensive way; to make a mess of. [Prov. Eng.; Colloq. U.S.]