From BiblePortal Wikipedia

Fausset's Bible Dictionary [1]

A Hamite name ("great hero".) Some of the Assyrian kings pretended descent from him. In the monuments he is called "the great brother," "the storm ruler," "king of battle," "the strong begetter"; "god of the chase," which is his special attribute. Nimrod deified, "the mighty hunter before the Lord," from whom naturally the kings of Babylon and Nineveh would claim descent. Cutha or Tiggaba (Nimrod's city in Arab tradition) is in the inscriptions especially dedicated to him. In accurate conformity with this the men of Cutha ( 2 Kings 17:30) planted by the Assyrian king as colonists in Samaria "made Nergal their god."

Nergal appears in the compound Nergal-sharezer ( Jeremiah 39:3;  Jeremiah 39:13). A human headed lion with eagles' wings was his symbol. His Semitic name Aria (which when transposed is Νir ) means "lion"; Greek Ares; Mars is his planet. Nerig is still its Mendaean name, and the Mendaeans call the third day of the week from him. The lion as lord of the forest was a fit symbol of the god of the chase. Tiglath Pileser (1150 B.C.) attributes to his gift the arrows wherewith he slew wild beasts; so Assur-dani-pal or Sardanapalus. Pul sacrificed to Nergal in Cutha, and Sennacherib built a temple to him in Tarbisa near Nineveh.

American Tract Society Bible Dictionary [2]

One of the gods of the Cuthite heathen who were transplanted into Palestine,  2 Kings 7:20 . This idol probably represented the planet Mars, which was ever the emblem of bloodshed. Mars is names, by the Zabians and Arabians, ill luck, misfortune. He was represented as holding in one had a drawn sword, and in the other, by the hair, a human head just cut off; his garments were blood red, as the light of the planet is also reddish. His temple among the Arabs was painted red; and they offered to him garments sprinkled with blood, and also a warrior, (probably a prisoner,) who was cast into a pool. The name Nergal appears in the proper names Nergalsharezer. Neriglassar,  Jeremiah 39:3,13 .

Hastings' Dictionary of the Bible [3]

NERGAL. The god of the city of Cubta in Babylonia, hence worshipped by the captive Cuthæans who were transplanted to Samaria by Sargon (  2 Kings 17:30 ). In the Bab. [Note: Babylonian.] -Assyr. [Note: Assyrian.] pantheon he was a god of war and pestilence, and of hunting, and the planet Mars was sacred to him.

The name Nergal is probably of Sumerian origin, namely, Ner-gal ‘great warrior.’ The god is sometimes in the non-Semitic texts called Ner-unu-gal , ‘hero of the lower world,’ evidently indicating his connexion with death and destruction.

W. M. Nesbit.

People's Dictionary of the Bible [4]

Nergal ( Ner'Gal ), Man-Devourer, Great Hero. An idol of the Cuthites.  2 Kings 17:30. The Jewish rabbins fancied that this idol was figured by a cock. It is now very commonly supposed to be the planet Mars. The word is used in titles, as Nergal-sharezer, the name of two princes of Babylon.  Jeremiah 39:8;  Jeremiah 39:13.

Smith's Bible Dictionary [5]

Ner'gal. (Hero). One of the chief Assyrian and Babylonian deities, seems to have corresponded closely to the classical Mars.  2 Kings 17:30. It is conjectured that he may represent the deified Nimrod.

Morrish Bible Dictionary [6]

An Assyrian and Babylonian god.  2 Kings 17:30 . It has many titles on the monuments, such as 'the god of the chase,' 'the king of battle,' etc.

Hawker's Poor Man's Concordance And Dictionary [7]

An idol of the men of Cuth, ( 2 Kings 17:30) compounded of Ner and Gal, light discovered.

Holman Bible Dictionary [8]

 2 Kings 17:30 Jeremiah 39:3 39:13

Easton's Bible Dictionary [9]

 2 Kings 17:30

Kitto's Popular Cyclopedia of Biblial Literature [10]

Ner´gal. Recent inquiries into the astrolatry of the Assyrians and Chaldæans have led to the conclusion that Nergal is one of the names for the planet Mars. This name of the planet, both among the Zabians and Arabians, means ill-luck, misfortune; and it was by no means peculiar to the mythology of the West to make it the symbol of bloodshed and war. Among the people first named, the planet Mars was typified under the figure of a man holding in one hand a drawn sword, and in the other a human head just cut off; and his garments were also red, which, as well as the other ideas attached to this idol, were no doubt founded on the reddish hue which the body of the planet presents to the eye. Among the southern Arabs his temple was painted red; and they offered to him garments stained with blood, and also a warrior (probably a prisoner), who was cast into a pool.

International Standard Bible Encyclopedia [11]

nâr´gal ( נרגל , nēreghal ): A B abylonian deity, identified with the planet Mars, and worshipped at Cutha (compare  2 Kings 17:30 ). See Babylonia And Assyria , Religion Of .

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [12]

Bibliography Information McClintock, John. Strong, James. Entry for 'Nergal'. Cyclopedia of Biblical, Theological and Ecclesiastical Literature. Harper & Brothers. New York. 1870.