From BiblePortal Wikipedia

Hastings' Dictionary of the Bible [1]

NISROCH. An Assyr. [Note: Assyrian.] deity in whose temple Sennacherib was worshipping when assassinated (  2 Kings 19:37 ,   Isaiah 37:38 ).

Gesenius compared the name with the Arabic nisr (‘eagle), and conjectured that it referred to one of the eagle-headed divinities that appear in the bas-reliefs. In later times attempts have been made to identify Nisroch with Nusku (the fire-god) whose name would naturally be most familiar in the construct form Nusuk , and even with Marduk. But Nusku did not at this period occupy a sufficiently prominent position in the Assyr. [Note: Assyrian.] pantheon; and the idea of Marduk, the great god of Babylon, being the patron of Sennacherib, the arch-enemy of that city, is manifestly incongruous. The deity that should logically hold this place is Ashur. Accordingly Prince suggests that Nisroch is a hybrid form due to a confusion of Ashur with Nusku . But comparison with the Greek forms seems to indicate that the original reading was something similar to Asorach . This Schrader explains as Ashurach , a hypothetical lenghtened form of Ashur. And Meinhold conjectures a compound ( Ashur-Aku ) of Ashur with Aku , the Sumerian name of the moon-god, whose Assyr. [Note: Assyrian.] name Sin is an element in the name Sennacherib .

W. M. Nesbit.

Fausset's Bible Dictionary [2]

The god of Nineveh, in whose temple Sennacherib was assassinated by his sons ( 2 Kings 19:37;  Isaiah 37:38). From Nisr Arabic (Hebrew Nesher , "eagle"), with the intensive Och , "the great eagle." The eagle headed human figure that overcomes the lion or bull, depicted in colossal size upon the walls and the portals, and in the groups upon the embroidered robes; a type of the supreme God. Philo Bybl. in Eusebius, Praepar. Evang. i. 10 says first Zoroaster taught that Ormuzd the Persian god was symbolized by the eagle's head. The constellation Aquila represented it.

Nisroch may be a corruption for Asarak, Assar (related to Asshur), an Assyrian god met with in many Assyrian proper names. Septuagint in many copies have for N. Asorach, Esorach, for which Josephus (Ant. 10:1, section 5) has Araskes. Sir H. Rawlinson says "Asshur had no temple in Nineveh in which Sennacherib could have been worshipping." Jarchi explains Nisroch "a beam of Noah's ark." Nisroch is apparently the eagle headed winged figure, with cone in one hand and basket in the other, taken from the N.W. palace, Nimrud. G. Rawlinson says Nisr is not found with this meaning, and Nisroch nowhere in the inscriptions; Nisroch he regards as a corruption.

American Tract Society Bible Dictionary [3]

A god of the Assyrians, in whose temple, and in the very act of idolatry, Sennacherib was slain by his own sons,  2 Kings 19:37 . According to the etymology, the name would signify "the great eagle;" and the earlier Assyrian sculptures recently exhumed at Nineveh have many representations of an idol in human form, but with the head of an eagle, as shown above. Among the ancient Arabs also the eagle occurs as an idol. The other accompanying cut, representing a winged figure in a circle, armed with a bow, is frequently met on the walls of ancient Nineveh in scenes of worship, and is believed to be an emblem of the supreme divinity of the Assyrians.

Smith's Bible Dictionary [4]

Nis'roch. (The Great Eagle). An idol of Nineveh, in whose temple, Sennacherib was worshipping, when assassinated by his sons, Adrammelech and Shizrezer.  2 Kings 19:37;  Isaiah 37:38. This idol is identified with the eagle-headed human figure, which is one of the most prominent on the earliest Assyrian monuments, and is always represented as contending with, and conquering, the lion or the bull.

People's Dictionary of the Bible [5]

Nisroch ( Nĭsrŏch ), Great Eagle? An Assyrian deity in whose temple at Nineveh Sennacherib was murdered by his sons, Adrammelech and Sharezer.  2 Kings 19:37;  Isaiah 37:38.

Watson's Biblical & Theological Dictionary [6]

a god of the Assyrians. Sennacherib was killed by two of his sons, while he was paying his adorations in the temple of this deity,  2 Kings 19:37;  Isaiah 37:38 . It is uncertain who this god was.

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

An idol of the Assyrians—derived from the same root as Nisan, but not an Hebrew derivation. ( 2 Kings 19:37)

Morrish Bible Dictionary [8]

An Assyrian idol, in the temple of which at Nineveh Sennacheribwas slain.  2 Kings 19:37;  Isaiah 37:38 .

Easton's Bible Dictionary [9]

Nesher   2 Kings 19:37 Isaiah 37:38

Holman Bible Dictionary [10]

 2 Kings 19:37 Isaiah 37:38

International Standard Bible Encyclopedia [11]

nis´rok , niz´rok ( נסרך , niṣrōkh ): The Assyrian god in whose temple Sennacherib was worshipping when put to death by his sons (  2 Kings 19:37;  Isaiah 37:38 ). The name is not found elsewhere. Some identify him with Asshur, the national deity. See Babylonia And Assyria , Religion Of .

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [12]

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

Kitto's Popular Cyclopedia of Biblial Literature [13]

Nis´roch, an idol of the Ninevites . The word is now usually supposed to mean 'great eagle.' This bird was held in peculiar veneration by the ancient Persians; and was likewise worshipped by the Arabs before the time of Mohammed.