one-way

from WordNet (r) 3.0 (2006)

one-way
    adj 1: moving or permitting movement in one direction only;
           "one-way streets"; "a one-way ticket"

from The Collaborative International Dictionary of English v.0.48

one-way \one-way\ adj.
   1. Legally permitting movement or travel in one direction
      only; -- of paths, especially roads; as, one-way streets.
      [WordNet 1.5]

   2. (Transportation) Pertaining to or valid for transportation
      in one direction between two points; as, a one-way ticket;
      a one-way fare. Opposed to {round-trip}.
      [PJC]