"Wormwood" is the name of a star in Revelation 8:10-11: “The third angel sounded his trumpet, and a great star, blazing like a torch, fell from the sky on a third of the rivers and on the springs of water—the name of the star is Wormwood. A third of the waters turned bitter, and many people died from the waters that had become bitter.” This is the third of the “trumpet judgments” described in Revelation. The seven trumpets are the judgments of the seventh seal (Revelation 8:1-5). The first trumpet causes hail and fire that destroy much of the plant life in the world (Revelation 8:7). The second trumpet brings about what seems to be a meteor, comet, or other heavenly body hitting the oceans and causing the death of one-third of the world’s sea life (Revelation 8:8-9). The third trumpet is similar to the second, except it affects the world’s lakes and rivers instead of the oceans (Revelation 8:10-11). It will cause a third part of all fresh water on earth to turn bitter and many people will die from drinking it.
The word wormwood is mentioned only here in the New Testament, but it appears eight times in the Old Testament, each time associated with bitterness, poison and death. The Revelation passage may not be saying that the star falling to the earth will actually be called Wormwood by the inhabitants of the earth. Rather, wormwood was a well-known bitter herb in the Bible times, so by naming the star Wormwood, we are told that its effect will be to embitter the waters of the earth, so much so that the water is undrinkable. It won’t be a matter of simply a bitter taste to the water; it will literally be poisonous. If drinking water is unavailable to one third of the earth’s population, it’s easy to see how chaos and terror will result. Humans can only survive about three days without water, and the inhabitants of the affected areas will be so desperate as to actually drink the poisoned water, causing the death of thousands, if not millions of people.
This is a prophecy that is yet to come in the last seven years of this age, also known as the 70th week of Daniel. This is only one of the natural disasters in the seven trumpets that will usher in the rise of the Antichrist to world power very quickly (see Revelation, chapter 13). Since one-third of the earth is destroyed by these trumpet judgments, this is only a partial judgment from God. His full wrath is yet to be unleashed.