mitochondria meaning
U.S. National Library of Medicine (5.00 / 1 vote) Rate this definition: Mitochondria. Semiautonomous, self-reproducing organelles that occur in the cytoplasm of all cells of most, but not all, eukaryotes. Each mitochondrion is surrounded by a double limiting membrane. The inner membrane is highly invaginated, and its projections are called cristae.