noun
1 dialect The cutting edge of a newly-forged blade hardened by fire. Chiefly figurative: keenness, freshness, or vitality; the quality of being hard, stern, or inflexible.
2The outer extent of a wildfire, especially the leading edge.
Origin
Late 16th century; earliest use found in John Knox (c1514–1572), religious reformer. From fire + edge.
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