of Nimrod "before the Lord" means......

"The phrase "before the Lord" in Hebrew is  ḡibbōr-ṣayiḏ lip̄nê Yahweh. This literally means something like "in the face of the Lord", according to my Hebrew concordance. Nimrod's life "before the Lord" is taken to mean he was brazenly bold in his opposition to God.

Genesis 10:9. Nimrod was a mighty hunter — In the Septuagint it is, He was a giant hunter: — the Arabic has it, He was a terrible giant before the Lord: and the Syriac, He was a great warrior.  

It is probable he began with hunting, and for this became famous to a proverb. 

   He served his country by ridding it of wild beasts, 

   and so insinuating himself into the affections of his neighbors, 

   he got to be their prince. 

And perhaps, 

   under pretense of hunting, 

   he gathered men under his command, 

   to make himself master of the country. 

Thus he became a mighty hunter, a violent invader of his neighbors’ rights and properties." 

BonifaceUSC/BensonCommentary