Ray1  n. 1 single line or narrow beam of light from a small or distant source. 2 straight line in which radiation travels to a given point. 3 (in pl.) Radiation of a specified type (x-rays). 4 trace or beginning of an enlightening or cheering influence (ray of hope). 5 any of a set of radiating lines, parts, or things. 6 marginal floret of a composite flower, e.g. A daisy. [latin *radius]