The Collaborative International Dictionary of English v.0.48:

Interurban \In`ter*ur"ban\ ([i^]n`t[~e]r*[^u]r"ban), a.
   Going between, or connecting, cities or towns; as, interurban
   electric railways.
   [Webster 1913 Suppl.]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "interurban":
   Amtrak, baggage train, burghal, cable railroad, choo-choo,
   citified, city, civic, cog railroad, cog railway, downtown, el,
   electric, electric train, elevated, express, express train, flier,
   freight, freight train, freighter, funicular, goods train,
   lightning express, limited, local, metro, metropolitan, midtown,
   milk train, monorail, municipal, oppidan, parliamentary,
   parliamentary train, passenger train, rack-and-pinion railroad,
   railroad train, rattler, rolling stock, shuttle, shuttle train,
   special, streamliner, suburban, subway, town, train, tube,
   underground, uptown, urban, village, way train