The Collaborative International Dictionary of English v.0.48:

Marchpane \March"pane`\, n. [Cf. It. marzapane,Sp. pan,.
   massepain, prob. fr. L. maza frumenty (Gr. ma^za) + L. panis
   bread; but perh. the first part of the word is from the name
   of the inventor.]
   A kind of sweet bread or biscuit; a cake of pounded almonds
   and sugar. Called also marzipan. [Obs.] --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

marzipan \mar"zi*pan`\ (m[aum]r"z[i^]*p[a^]n`), n.
   A confection made of almonds and sugar mixed into a paste and
   molded into shapes. Same as marchpane.
   [PJC]

WordNet (r) 3.0 (2006):

marzipan
    n 1: almond paste and egg whites [syn: marzipan, marchpane]