Burning fiercely or shining intensely; extremely fast or intense.
From blaze + -ing, where 'blaze' comes from Middle English blase, possibly from Old Norse blys 'torch.' The figurative sense of 'very fast' (as in 'blazing speed') developed in the 19th century.
The word 'blazing' perfectly captures how we use fire metaphors for intensity - blazing trails, blazing speed, blazing hot! Interestingly, 'blaze' also means the white mark on a horse's face, which comes from the same root meaning 'bright spot.'
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