1.
If something such as a radio aerial, microphone, or loudspeaker is ~, it works most effectively in one direction, rather than equally in all directions at once. (TECHNICAL)
Dish aerials are highly ~...
ADJ
2.
Directional means relating to the direction in which something is pointing or going. (TECHNICAL)
Jets of compressed air gave the aircraft lateral and ~ stability.
ADJ: usu ADJ n