The Collaborative International Dictionary of English v.0.48:

Limousine \Li`mou*sine"\, n. [Cf. F. limousine a kind of cloak,
   fr. Limousin, an old province in central France.]
   an elongated, luxurious automobile, designed to be driven by
   a chauffeur and often having a glass partition between the
   driver's seat and the passengers' compartment behind.

   Note: When intended for use in transporting businessmen, the
         limousine may be equipped with a telephone and other
         conveniences to permit work during travel. Limousines
         are often rented for travel to and from airports, and
         as a luxurious perquisite on special occasions, as
         weddings or school prm nights. Originally (1913) the
         term referred to an automobile body with seats and
         permanent top like a coup['e], and with the top
         projecting over the driver and a projecting front, or
         an automobile with such a body.
         [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

limousine
    n 1: large luxurious car; usually driven by a chauffeur [syn:
         limousine, limo]