What does "sea cow" mean?

Any of several marine mammals of the order Sirenia, including the manatee and dugong.

What is a synonym for "sea cow"?

Common synonyms include: manatee, manatees, sirenian, sirenian mammal.

noun

noun ·Rare ·Advanced level

Noun

1
Any of several marine mammals of the order Sirenia, including the manatee and dugong.
2
any of two families of large herbivorous aquatic mammals with paddle-shaped tails and flipper-like forelimbs and no hind limbs wordnet

From sea + cow.