Merriam-Webster Collegiate Dictionary - chlorophyll

 noun  Etymology: French ~e, from chlor- + Greek phyllon leaf — more at blade  Date: 1819  1. the green photosynthetic pigment found chiefly in the chloroplasts of plants and occurring especially as a blue-black ester C55H72MgN4O5 or a dark green ester C55H70MgN4O6 — called also respectively ~ a, ~ b  2. a waxy green ~-containing substance extracted from green plants and used as a coloring agent or deodorant  • ~ous adjective