Why does the Torah refer to Nimrod as "Gibor Tzayid - mighty hunter"?
Rashi: Because the word "Tzayid" literally means "trap (hunt)" - and (like Esav 1 ), Nimrod would trap people (verbally) to do his bidding.
Ramban #1: Nimrod was the first self- declared monarch to rule over others by force. 2 Until his time, there had been no wars and no kings. First he overpowered the men of Bavel; then he did the same to Ashur, where he built the cities mentioned in the current Pesukim.
Ramban #2 and Ibn Ezra: He was an outstanding hunter. 3
In connection with whom the Torah uses the same word (See Bereishis 25:27, and Rashi there). See Da'as Zekenim to Bereishis 25:30; and Rashi to Pesachim 54b, DH 'Bigdo Shel Adam ha'Rishon' - it was Esav who ultimately killed Nimrod and assumed his role.
See also Ba'al ha'Turim.
What is the significance of the words "Lifnei HaSh-m"?
Rashi: This means that Nimrod acted deliberately to anger HaSh-m (not for his own benefit), "He knew his Master and had in mind to rebel against Him."
Seforno: It is another way of saying, "extremely mighty." 1
Rashbam: It means the greatest in the world.
Ramban: It means that there was nobody in the entire world who could match his strength.
Ibn Ezra: 2 After hunting the wild animals, he would build altars and sacrifice them to HaSh-m. 3
Gur Aryeh: Refer to 10:8:1.4:1.
What is the significance of the phrase "Therefore people would say, 'Like Nimrod, a Gibor Tzayid before HaSh-m!' "?
Rashi: Nimrod became synonymous with rebellion, and people would say about anyone who was brazenly evil, who knew of HaSh-m and rebelled against Him intentionally, "he is like Nimrod the mighty hunter!"
