The Collaborative International Dictionary of English v.0.48:

Muscat \Mus"cat\, n. [F. See Muscadel.] (Bot.)
   A name given to several varieties of Old World grapes,
   differing in color, size, etc., but all having a somewhat
   musky flavor. The muscat of Alexandria is a large oval grape
   of a pale amber color. [Written also muskat.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

muscat
    n 1: any of several cultivated grapevines that produce sweet
         white grapes [syn: muscat, muskat]
    2: a port on the Gulf of Oman and capital of the sultanate of
       Oman [syn: Muscat, Masqat, capital of Oman]
    3: wine from muscat grapes [syn: muscat, muscatel,
       muscadel, muscadelle]
    4: sweet aromatic grape used for raisins and wine [syn:
       muscat, muscatel, muscat grape]