a flame: the bright, leaping tongue of a burning fire, the part of a fire you can see and feel
Greek had a general word for fire, πῦρ, which covers the whole burning thing: the element, the heat, the destruction. This word is narrower and more visual. It names the blaze itself, the moving tongue of light standing above whatever is burning. That is why it can be pointed at and described, and why writers reach for it when they want a reader to picture something rather than simply know that fire is present.
Six of its seven uses in the New Testament stand next to the word for fire, giving "a flame of fire" or "blazing fire". In English that sounds like saying the same thing twice, but in Greek it was an ordinary and vivid way of speaking, and it carries over from the Greek Old Testament, where the same pairing describes the bush that burned in front of Moses without being eaten up. So the doubled phrase is a habit of speech, not a special technical term.
The seven places it appears fall into a narrow but striking range:
- the flame that scorches a rich man in the place of the dead
- the fire in the bush where God speaks to Moses in the desert
- the blaze that surrounds Jesus when he is revealed from heaven
- the burning look of God's servants and of the eyes of the risen Christ
What holds these together is one picture used in different settings. A flame is bright, it moves, it cannot be touched without pain, and it shows where something powerful is at work. When the last book of the Bible says the eyes of the risen Christ were like a flame of fire, it is drawing on all of that at once: light that sees, heat that judges, and a presence no one can casually approach.