Quick answer
Tiamat is a girl name meaning "sea".
Pronunciation: English /ˈti.ə.mɑt/.
Meaning and history
From Akkadian tâmtu meaning "sea". In Babylonian myth Tiamat was the personification of the sea, appearing in the form of a huge dragon. By Apsu she gave birth to the first of the gods. Later, the god Marduk (her great-grandson) defeated her, cut her in half, and used the pieces of her body to make the earth and the sky.
Notes and context
Usage: semitic mythology