The Collaborative International Dictionary of English v.0.48:

Talcum \Tal"cum\ (t[a^]l"k[u^]m), n. [NL.] (Min.)
   Same as Talc.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

talcum
    n 1: a fine grained mineral having a soft soapy feel and
         consisting of hydrated magnesium silicate; used in a
         variety of products including talcum powder [syn: talc,
         talcum]
    2: a toilet powder made of purified talc and usually scented;
       absorbs excess moisture [syn: talcum, talcum powder]