Meaning
"the region of departed spirits of the lost" (but including the blessed dead in periods preceding the ascension of Christ). It has been thought by some that the word etymologically meant "the unseen" (from a, negative, and eido, "to see"), but this derivation is questionable; a more probable derivation is from hado, signifying "all-receiving." It corresponds to "Sheol" in the OT. In the AV of the OT and NT; it has been unhappily rendered "hell," e.g., Psa 16:10; or "the grave," e.g., Gen 37:35; or "the pit," Num 16:30, Num 16:33; in the NT the revisers have always used the rendering "hades;" in the OT, they have not been uniform in the translation, e.g. in Isa 14:15 "hell" (marg., "Sheol"); usually they have "Sheol" in the text and "the grave" in the margin. It never denotes the grave, nor is the permanent region of the lost; in point of time it is, for such, intermediate between decease and the doom of Gehenna. For the condition, see Luk 1:16-31.
The word is used four times in the Gospels, and always by the Lord, Mat 11:23, Mat 16:18, Luk 10:15, Luk 16:23; it is used with reference to the soul of Christ, Act 2:27, Act 2:31; Christ declares that He has the keys of it, Rev 1:18; in Rev 6:8 it is personified, with the signification of the temporary destiny of the doomed; it is to give up those who are therein, Rev 20:13, and is to be cast into the lake of fire, Rev 20:14.
Note: In 1Co 15:55 the most authentic mss. have thanatos, "death," in the 2nd part of the verse, instead of "hades," which the AV wrongly renders "grave" ("hell," in the marg.).