The Collaborative International Dictionary of English v.0.48:

eastbound \eastbound\ adj.
   1. moving toward the east; as, eastbound trains.

   Syn: eastward.
        [WordNet 1.5]

   2. designated for traffic moving toward the east; -- of lanes
      in roads or railroads, or other traffic lanes; as, the
      eastbound lanes of Interstate 80 are blocked by an
      overturned tractor-trailer; the train will leave on
      eastbound platform 5.
      [PJC]

WordNet (r) 3.0 (2006):

eastbound
    adj 1: moving toward the east; "eastbound trains" [syn:
           eastbound, eastward]