Source : Webster's Revised Unabridged Dictionary (1913)

muckrake \muck"rake`\, in the above sense, and the noun
muckraker \muck"rak`er\, to designate one so engaged, were
   speedily coined and obtained wide currency. The original
   allusion was to a character in Bunyan's ``Pilgrim's
   Progress'' so intent on raking up muck that he could not see
   a celestial crown held above him. Mucoid \Mu"coid\, n. [Mucin
   + -oid.] (Physiol. Chem.)
   One of a class of mucinlike substances yielding on
   decomposition a reducing carbohydrate together with some form
   of proteid matter.

Source : WordNet®

muckraker
     n : one who spreads real or alleged scandal about another
         (usually for political advantage) [syn: {mudslinger}]