unidirectional

1. not comparablePertaining to only one direction, e.g.: where all component parts are aligned in the same direction in space.

   [...] a reversible booster was fitted to the trailing bogie; all previous applications on the L.N.E.R. for use in main line traffic had been of unidirectional boosters, […]

   1941 November, O. S. Nock, “The Locomotives of Sir Nigel Gresley: Part VI—Experiments and Rebuilds 1927-33”, in Railway Magazine, page 483

   1 more example

   Equally important is the class mailing list, which facilitates two-way communication at a distance. (By contrast, the web page is basically a unidirectional teacher-to-student communication.)

   2005, Richard Samson, edited by Martha Tennent, Training for the New Millennium: Pedagogies for translation and interpreting, Benjamins Translation Library, page 119

   Synonyms: simplex

2. not comparableNot subject to change or reversal of direction.

plural unidirectionals

1. A fabric in which the majority of fibers run in the same single direction.