Commentaries:
Robertson's Word Pictures (NT)
A strong angel (eiv aggelov isxurov). Here eiv = a, just an indefinite article, not "one" as a numeral.
Took up (hren). First aorist active indicative of airw.
As it were a great millstone (wv mulinon megan). Late adjective, in inscriptions, here only in N.T., made of millstone (mulov, Matthew 18:6; Revelation 18:22), while mulikov (Luke 17:2) means belonging to a mill. This is not a small millstone turned by women (Matthew 24:41), but one requiring an ass to turn it (Mark 9:42), and so "a great" one.
Cast (ebalen). Second aorist active of ballw, to hurl.
With a mighty fall (ormhmati). Instrumental case (manner) of ormhma, a rush, old word from ormaw, to rush (Matthew 8:32), here only in N.T.
Shall be cast down (bleqhsetai). Future (first) passive of ballw, the same verb (ebalen), effective punctiliar future. Like a boulder hurled into the sea.
Shall be found no more at all (ou mh eureqh eti). Double negative with first aorist passive subjunctive of euriskw. See Revelation 9:6 for ou mh with the active voice of euriskw. Already the old Babylon was a desert waste (Strabo, XVI. 1073).
Other Robertson's Word Pictures (NT) entries containing Revelation 18:21:
Revelation 5:2
Revelation 8:13
Revelation 10:1
Revelation 11:8
Revelation 14:8
Revelation 18:22
Revelation 18:23
Revelation 19:3
Revelation 19:17
DISCLAIMER: Church of the Great God (CGG) provides these resources to aid the individual in studying the Bible. However, it is up to the individual to "prove all things, and hold fast to that which is good" (I Thessalonians 5:21). The content of these resources does not necessarily reflect the views of CGG. They are provided for information purposes only.