Erum (ערום or Arum), (plural erumim ערומים) is a Hebrew word meaning "cautious, cunning, subtle, crafty, or prudent".
Note: The consensus of the Biblical commentators in classical Judaism is that the "serpent" of the narrative in the Book of Genesis, was literally a serpent. They differ regarding what force it represented: The "evil inclination", "Satan", or the "Angel of Death". According to the Midrash, before this cunning beast was cursed, it stood erect and was endowed with some faculty of communication.
References
Erum (Hebrew) Wikipedia(Text) CC BY-SA