Source : Webster's Revised Unabridged Dictionary (1913)

Scallion \Scal"lion\, n. [OF. escalone, eschaloingne, L. caepa
   Ascalonia onion of Ascalon; caepa onion + Ascalonius of
   Ascalon, fr. Ascalo Ascalon, a town in Palestine. Cf.
   {Shallot}.]
   1. (Bot.) A kind of small onion ({Allium Ascalonicum}),
      native of Palestine; the eschalot, or shallot.

   2. Any onion which does not ``bottom out,'' but remains with
      a thick stem like a leek. --Amer. Cyc.

Source : WordNet®

scallion
     n 1: plant having a large slender white bulb and flat overlapping
          dark green leaves; used in cooking; believed derived
          from the wild Allium ampeloprasum [syn: {leek}, {Allium
          porrum}]
     2: young onion before the bulb has enlarged [syn: {green onion}]