- The male germ cell in animals and plants, the
essential element in fertilization; a microscopic animalcule-like
particle, usually provided with one or more cilia by which it is
capable of active motion. In animals, the familiar type is that of a
small, more or less ovoid head, with a delicate threadlike cilium, or
tail. Called also spermatozoon. In plants the more usual term is
antherozoid.