The Collaborative International Dictionary of English v.0.48:

Alopecia \Al`o*pe"ci*a\ ([a^]l`[-o]*p[=e]"sh[i^]*[.a]), Alopecy
\A*lop"e*cy\ ([.a]*l[o^]p"[-e]*s[y^]), n. [L. alopecia, Gr.
   'alwpeki`a, fr. 'alw`phx fox, because loss of the hair is
   common among foxes.] (Med.)
   Loss of the hair; baldness. AS
   [1913 Webster]

WordNet (r) 3.0 (2006):

alopecia
    n 1: loss of hair (especially on the head) or loss of wool or
         feathers; in humans it can result from heredity or hormonal
         imbalance or certain diseases or drugs and treatments
         (chemotherapy for cancer)