on fire

From Middle English on fier, on fijre, on fire, on fyire, on fyre.

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on fire

1. Being burned by fire.

   Synonyms: afire, aflame, alight, burning, flaming, in flames, going up in smoke

   If the wind picks up and the flames spread, the whole town could go on fire.

2. (idiomatic) Overwhelmed with emotion; beside oneself.
   • 2022 [2021], Jill Bolte Taylor, “The Brain Huddle: Your Power Tool for Peace”, in Whole Brain Living: The Anatomy of Choice and the Four Characters That Drive Our Life, Carlsbad, CA: Hay House, →ISBN, page 160:

     Anytime I am on fire with anxiety about the future, or totally freaking out that I am not being seen, heard, or treated fairly based on my old wounds, it is easy for me to RECOGNIZE that my Character 2 has flared right up in an attempt to not only protect me but help me get my needs met.

3. (idiomatic) Excited, enthusiastic or passionate.
   • 1975 November 6, Robert E. Johnson, “The Prodigal Returns To His First Love: The Beauty Industry”, in Jet, volume 49, number 7, page 21:

     “I'm on fire with an idea,” the 48-year-old businessman proclaimed with excitement similar to that which he projected in 1971 when his company became the first predominantly Black-owned corporation to be listed on the American Stock Exchange.

4. (idiomatic) Doing very well; achieving good results at a rapid rate.

   Synonyms: on a roll, on a tear

   That striker has scored four goals so far – he's on fire!

5. (idiomatic, informal) Sexually aroused.
6. (hyperbolic, of a body part) Experiencing a burning-like sensation, especially "the burn" (from buildup of lactic acid)
   • 2016, Eric Fair, Consequence, page 28:

     He locks us into a crouched position that results in muscle failure of the quads, hamstrings, and calves. It hurts. We raise ten-pound rubber rifles and hold them parallel to the ground. Our legs are on fire, then our arms too.

• get on like a house on fire

• Jonathon Green (2024) “on fire adj.”, in Green’s Dictionary of Slang

• forein, infero-