adj. & n.
adj. (rapider, rapidest) 1 quick, swift. 2 acting or completed in a short time. 3 (of a slope) descending steeply. 4 Photog. fast.
n. (usu. in pl.) a steep descent in a river-bed, with a swift current. rapid eye-movement a type of jerky movement of the eyes during periods of dreaming. rapid-fire (attrib.) fired, asked, etc., in quick succession. rapid transit (attrib.) denoting high-speed urban transport of passengers. rapidity n. rapidly adv. rapidness n.
[ L rapidus f. rapere seize ]