Definitions of muck:

• noun:   fecal matter of animals
• noun:   any thick messy substance
• verb:   remove muck, clear away muck, as in a mine
• verb:   spread manure, as for fertilization
• verb:   soil with mud, muck, or mire

  Example: "The child mucked up his shirt while playing ball in the garden"

• name:  A surname (very rare: popularity rank in the U.S.: #19033)