NEPHILIM (Heb. nephilim; Numbers 13:13). The form of the Heb. word denotes a plural verbal adjective or noun of passive signification, certainly from napal, “to fall,” so that the connotation is “the fallen ones,” clearly meaning the unnatural offspring that were on the earth in the years before the Flood, “and also afterward, when the sons of God came in to the daughters of men, and they bore children to them” (Genesis 6:4). The mention of the great stature of the Nephilim, the sons of Anak, in the evil report that the ten spies brought of the land of Canaan (Numbers 13:33) together with the LXX rendering, gigantes, suggested the translation giants. They were exceedingly wicked and violent so that “every intent” of the thoughts of men’s hearts “was only evil continually” (Genesis 6:5). See Merrill F. Unger, Biblical Demonology, pp. 45-52. From The New Unger's Talking Bible Dictionary, electronic media.
(Genesis 6:4; Numbers 13:33). See also Giant. The Nephilim are considered by many to be giant demigods, the unnatural offspring of the “daughters of men” (mortal women) in cohabitation with the “sons of God” (angels; cf. Genesis 6:1-4). This utterly unnatural union, violating God’s created order of being, was such a shocking abnormality as to necessitate the worldwide judgment of the Flood. Another view of the Nephilim is that they were particularly violent (the name is from a root, “to fall,” i.e., on other people), strong (“mighty”), and infamous (“men of renown”) people who predated the marriages of v. 2. This viewpoint often explains the unions as intermarriage of the godly line of Seth (described in 4:25–5:32) with the ungodly line of Cain (4:1-24). From the book, The Bible Has the Answer, by Henry M. Morris and Martin E. Clark.