chlo·ro·phyll also chlo·ro·phyl (klôr'ə-fĭl, klōr'-) n. Any of a group of green pigments that are found in the chloroplasts of plants and in other photosynthetic organisms such as cyanobacteria, especially:
a. A waxy blue-black microcrystalline green-plant pigment, C55H72MgN4O5, with a characteristic blue-green alcohol solution. Also called chlorophyll a. chlo'ro·phyl'lous adj.