The Collaborative International Dictionary of English v.0.48:

Smegma \Smeg"ma\, n. [NL., fr. Gr. ???? soap, fr. ????? to wash
   off.] (Physiol.)
   The matter secreted by any of the sebaceous glands.
   Specifically:
   (a) The soapy substance covering the skin of newborn infants.
   (b) The cheesy, sebaceous matter which collects between the
       glans penis and the foreskin.
       [1913 Webster]

WordNet (r) 3.0 (2006):

smegma
    n 1: a white secretion of the sebaceous glands of the foreskin