le·vi·a·than 
(lə-vīə-thən)
(lə-vīə-thən)n.
1. Something unusually large of its kind, especially a ship.
2. A very large animal, especially a whale.
3. A monstrous sea creature mentioned in the Bible.
[Middle English, huge biblical sea creature, from Late Latin, from Hebrew liwyātān; see lwy in the Appendix of Semitic roots.]