The Collaborative International Dictionary of English v.0.48:

Afire \A*fire"\ ([.a]*f[imac]r"), adv. & a. [Pref. a- + fire.]
   On fire.
   [1913 Webster]

WordNet (r) 3.0 (2006):

afire
    adj 1: lighted up by or as by fire or flame; "forests set ablaze
           (or afire) by lightning"; "even the car's tires were
           aflame"; "a night aflare with fireworks"; "candles alight
           on the tables"; "houses on fire" [syn: ablaze(p),
           afire(p), aflame(p), aflare(p), alight(p), on
           fire(p)]

Moby Thesaurus II by Grady Ward, 1.0:

90 Moby Thesaurus words for "afire":
   abandoned, ablaze, aflame, aflicker, aglow, alight, ardent,
   blazing, boiling over, breathless, burning, candent, candescent,
   comburent, committed, conflagrant, cordial, dedicated, delirious,
   devoted, devout, drunk, earnest, enthusiastic, excited, exuberant,
   faithful, febrile, fervent, fervid, fevered, feverish, fiery,
   fired, flagrant, flaming, flaring, flickering, flushed, fuming,
   glowing, guttering, hearty, heated, hot, hot-blooded, ignescent,
   ignited, impassioned, in a blaze, in a glow, in earnest, in flames,
   incandescent, inflamed, inspired, intense, intent, intent on,
   intoxicated, keen, kindled, live, lively, living, loyal, on fire,
   passionate, perfervid, red-hot, reeking, resolute, scintillant,
   scintillating, serious, sincere, smoking, smoldering, sparking,
   spirited, steaming, steamy, unextinguished, unquenched,
   unrestrained, vehement, vigorous, warm, white-hot, zealous