(Hebrew תנין) An often debated term in the Hebrew scriptures, variously interpreted to mean, "whale, crocodile, serpent, leviathan, dinosaur," and more. The real meaning is revealed in Kabbalah. Study this lecture about the letter Nun.
"And God created great tanniyn , and every nephesh chaiah that creeps, which the mayim brought forth abundantly, after their kind, and every winged fowl after his kind: and God saw that [it was] good." - Genesis 1:21
"When Pharaoh shall speak unto you, saying, Shew a miracle for you: then thou shalt say unto Aaron, Take thy rod, and cast [it] before Pharaoh, [and] it shall become a tanniyn." - Exodus 7:9