Antichrist - Vine's Expository Dictionary of New Testament Words
Antichrist[ 1,,G500, antichristos ]
can mean either against Christ" or "instead of Christ," or perhaps, combining the two, "one who, assuming the guise of Christ, opposes Christ" (Westcott). The word is found only in John's epistles,
(a) of the many "antichrists" who are forerunners of the "Antichrists" himself, 1 John 2:18, 1 John 2:22; 2 John 1:7;
(b) of the evil power which already operates anticipatively of the "Antichrist," 1 John 4:3.
What the Apostle says of him so closely resembles what he says of the first beast in Rev. 13, and what the Apostle Paul says of the Man of Sin in 2 Thess. 2, that the same person seems to be in view in all these passages, rather than the second beast in Rev. 13, the false prophet; for the latter supports the former in all his Antichristian assumptions.
Note: The term pseudochristos, "a false Christ," is to be distinguished from the above; it is found in Matthew 24:24; Mark 13:22. The false Christ does not deny the existence of Christ, he trades upon the expectation of His appearance, affirming that he is the Christ. The Antichrist denies the existence of the true God (Trench, Syn. XXX).