From WordNet (r) 2.0 (August 2003) [wn]:
limo
n : large luxurious car; usually driven by a chauffeur [syn:
limousine]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
limo \limo\ n.
Limousine; -- a shortened form.
Syn: limousine.
[WordNet 1.5]