As a noun, we find it in B'reisheet 3:1 וְהַנָּחָשׁ, הָיָה עָרוּם
meaning: serpent. "And the serpent was subtle, crafty or shrewd." This is also the word for the serpent which Moshe's staff became before Pharoah, (Sh'mot 7) and the serpents that bit the people in the wilderness. (B'midbar 21)
As a noun, it can also mean: the constellation of the dragon, an incantation or omen.
As a verb, נחש meands "to practice sorcery to give oracles, to divine, to foretell". This is a command: לֹא תְנַחֲשׁוּ meaning: "do not practice divination". These words are throughout Torah, see V'yikra 19:26, D'varim 18:10. This is also the word used toward Yosef in B'reisheet 44:15. It is also found in M'lakhim Bet 17:17 in a list of things that are evil in the sight of ADONAI
תודה רבה לשילה מחתן שלי
Todah Raba lasheilah m'chatan sheli!
Thanks much for the question from my son-in-law!