What does 1 Corinthians 15:55 mean?

Paul is describing the moment when, at Christ's coming, every believer in Jesus, living and dead, will be transformed into glorified bodies to spend eternity with God. This is the moment all of creation is waiting for (Romans 8:19). This is the moment mentioned by the prophets of God. Paul referenced Isaiah 25:8 in the previous verse: "Death is swallowed up by victory."

Now he references Hosea 13:14 to taunt death about its coming once-and-for-all defeat: "O death, where is your victory? O death, where is your sting?"

It's true that Jesus' resurrection from the grave was the beginning of the end for death and the "one with the power of death, that is, the devil" (Hebrews 2:14), but for now believers still physically die. The moment we are given redeemed, glorified resurrection bodies is the instant described here: the end of the end for death. This will culminate in the complete and total elimination of death and evil (Revelation 20:14). For now, those who are in Christ will continue to experience an inner groaning, a sense of incompletion, until this longed-for moment, when our bodies are redeemed by this promised, death-defeating transformation (Romans 8:23).