The Collaborative International Dictionary of English v.0.48:

Cognate \Cog"nate\, a. [L. cognatus; co- + gnatus, natus, p. p.
   of nasci, anciently gnasci, to be born. See Nation, and cf.
   Connate.]
   1. Allied by blood; kindred by birth; specifically (Law),
      related on the mother's side.
      [1913 Webster]

   2. Of the same or a similar nature; of the same family;
      proceeding from the same stock or root; allied; kindred;
      as, a cognate language.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cognate \Cog"nate\, n.
   1. (Law) One who is related to another on the female side.
      --Wharton.
      [1913 Webster]

   2. One of a number of things allied in origin or nature; as,
      certain letters are cognates.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cognate
    adj 1: related in nature; "connate qualities" [syn: connate,
           cognate]
    2: having the same ancestral language; "cognate languages"
    3: related by blood [syn: akin(p), blood-related, cognate,
       consanguine, consanguineous, consanguineal, kin(p)]
    n 1: one related by blood or origin; especially on sharing an
         ancestor with another [syn: blood relation, blood
         relative, cognate, sib]
    2: a word is cognate with another if both derive from the same
       word in an ancestral language [syn: cognate, cognate
       word]