The Collaborative International Dictionary of English v.0.48:

Matricide \Mat"ri*cide\, n. [L. matricidium; mater mother +
   coedere to kill, slay: cf. F. matricide. See Mother, and
   cf. Homicide.]
   1. The murder of a mother by her son or daughter.
      [1913 Webster]

   2. [L. matricida: cf. F. matricide.] One who murders one's
      own mother.
      [1913 Webster]

WordNet (r) 3.0 (2006):

matricide
    n 1: a person who murders their mother
    2: the murder of your mother

Moby Thesaurus II by Grady Ward, 1.0:

19 Moby Thesaurus words for "matricide":
   aborticide, fratricide, fungicide, genocide, germicide, herbicide,
   homicide, infanticide, insecticide, microbicide, parricide,
   patricide, pesticide, regicide, rodenticide, sororicide, suicide,
   uxoricide, vermicide