organelle /ôrgənel″/ [Gk, organon, instrument] , 1. any one of various specialized macromolecular structures bound within most cells, such as the mitochondria, the Golgi apparatus, the endoplastic reticulum, the lysosomes, and the centrioles. 2. any one of the tiny structures of protozoa associated with locomotion, metabolism, and other processes. Also called organella.
