Source : Webster's Revised Unabridged Dictionary (1913)

Sirenian \Si*re"ni*an\, n. (Zo["o]l.)
   Any species of Sirenia.

Source : WordNet®

sirenian
     n : any of two families of large herbivorous aquatic mammals
         with paddle-shaped tails and flipper-like forelimbs and
         no hind limbs [syn: {sea cow}, {sirenian mammal}]