From WordNet (r) 3.0 (2006) [wn]:
downtown
adv 1: toward or in the lower or central part of town [ant:
uptown]
adj 1: of or located in the lower part of a town, or in the
business center; "downtown Manhattan"; "delinquents
roaming the downtown streets" [ant: uptown]
n 1: the central area or commercial center of a town or city;
"the heart of Birmingham's downtown" [syn: {business
district}, downtown]