Merriam-Webster Collegiate Dictionary - two-way

 adjective  Date: 1844  1. being a cock or valve that will connect a pipe or channel with either of two others  2. moving or allowing movement in either direction a ~ bridge  3.  a. involving or allowing an exchange between two individuals or groups there must be good ~ communication — Jerrold Orne; especially designed for both sending and receiving messages ~ radio  b. involving mutual responsibility or reciprocal relationships political alliance is a ~ thing — T. H. White †1986  4. involving two participants a ~ race  5. usable in either of two manners a ~ lamp