In this verse eight different kinds of people are listed who will be thrown into the lake of burning sulfur. It is not implied that all are exclusive categories; what is meant is that any person guilty of any one or more of these sins will suffer the second death. For a similar list see 22.15.
Cowardly: people who were not courageous and constant in their Christian witness. To express the idea of cowardly, many languages use vivid idiomatic expressions; for example, “white-eyed people” (Thai).
Faithless: apostates, those who had renounced, or given up, their Christian faith. This may be expressed in many languages as “stopped believing in Jesus” or “turned their backs on Jesus.”
Polluted: this refers to those who were guilty of gross sins or heathen worship; in Greek it is the passive participle of the verb meaning “to make foul”; the related noun “pollution,” “abomination,” is used in 17.4, 5; 21.27. Other ways to express this are “people who have made themselves dirty (or, unclean) through worshiping idols” or “people who have committed foul (or, dirty) sins.”
Murderers: those who deliberately kill others, not in warfare.
Fornicators: those who indulge in immoral sexual activity; the word occurs again in 22.15. It is probable that here the word carries its normal meaning and is not a figure for idolatry.
Sorcerers: see comments on “sorceries” in 9.21; 18.23. These are people who regular do “sorcery.”
Idolaters: see “worshiping … idols” in 9.20; the word appears also in 22.15.
All liars: as in 21.27 and 22.15, those who lie are condemned to hell. See also 3.9.
Their lot shall be in the lake: here lot means destiny, which is condemnation and punishment. “They will be condemned to the lake,” or “they will be punished by being thrown into the lake,” or “I will punish them by throwing them into the lake.”
The lake that burns with fire and sulphur: see 19.20; 20.10.
The second death: see 20.14.
Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on The Revelation to John. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .