- an aquatic, herbivorous mammal of the order Sirenia, including the manatee and dugong.
- of, relating to, or belonging to the Sirenia, an order of aquatic herbivorous placental mammals having forelimbs modified as paddles, no hind limbs, and a horizontally flattened tail: contains only the dugong and manatees
- any animal belonging to the order Sirenia; a sea cow
