The Collaborative International Dictionary of English v.0.48:

Mulier \Mu"li*er\, n. [L., a woman.]
   1. A woman.
      [1913 Webster]

   2. (Law)
      (a) Lawful issue born in wedlock, in distinction from an
          elder brother born of the same parents before their
          marriage; a lawful son.
      (b) (Civ. Law) A woman; a wife; a mother. --Blount.
          --Cowell.
          [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

MULIER. A woman, a wife; sometimes it is used to designate a marriageable
virgin, and in other cases the word mulier is employed in opposition to
virgo. Poth. Pand. tom. 22, h.t. In its most proper signification, it means
a wife.
     2. A son or a daughter, born of a lawful wife, is called filius
mulieratus or filia mulierata, a son mulier, or a daughter mulier. The term
is used always in contradistinction to a bastard; mulier being always
legitimate. Co. Litt. 243.
     3. When a man has a bastard son, and afterwards marries the mother, and
has by her another son, the latter is called the mulier puisne. 2 Bl. Com.
248.