n. Exposure to the sun's rays; subjection to the influence of solar heat and light, as for drying, maturing, or the production of chemical action; in medicine, treatment by exposure to the sun, in order to stimulate the vital forces.n. A local injury of plants caused by exposure to too strong light, or to the rays of the sun concentrated as by inequalities in the glass of a greenhouse, producing excessively rapid evaporation which kills the part affected.n. The state of being heated by the sun; the effect of exposure to the sun's rays; specifically, as applied to persons, sunstroke.