1rare A small room or cell.
In later use chiefly in French-speaking contexts.
A small space, cavity, or sac in an organism or natural product.
Late Middle English (in an earlier sense). From Middle French, French cellule extremely small enclosed space, cavity, or sac in an organized body or product, compartment in the brain, small room or cell and its etymon classical Latin cellula small room or cell, in post-classical Latin also compartment in the brain from cella + -ula; compare -ule.