directional

[dih-rek-shuh-nl, dahy-]
adjective
  1. of, relating to, or indicating direction in space.
  2. Radio. adapted for determining the direction of signals received, or for transmitting signals in a given direction: a directional antenna.
  3. of, relating to, or providing guidance or leadership.

Origin of directional

First recorded in 1605–15; direction + -al1
Related formsdi·rec·tion·al·i·ty, noundi·rec·tion·al·ly, adverbun·di·rec·tion·al, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for undirectional

directional

adjective
  1. of or relating to a spatial direction
  2. electronics
    1. having or relating to an increased sensitivity to radio waves, sound waves, nuclear particles, etc, coming from a particular direction
    2. (of an aerial) transmitting or receiving radio waves more effectively in some directions than in others
  3. physics electronics
    1. concentrated in, following, or producing motion in a particular direction
    2. indicating direction
  4. indicating the direction something, such as a fashion trend, might takedirectional fashion looks
Derived Formsdirectionality, noun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012