The word was struck out in the Etymologies, but is well attested in late compounds such as Mormegil or Arvegil (with regular mutation). It is conceivably the Sindarinized form of Quenya makil, coexisting with magol (see tegil and tegol for a similar case)
_ n. _sword. i·arben na megil and 'The Knight of the Long Sword'.
(as metal) 1) malad (i valad), pl. melaid (i melaid) if there is a pl. 2) malt (i valt), pl. melt (i melt) if there is a pl. (VT42:27). ”Gold” in extended senses: glawar (i **lawar) (sunlight, radiance of the Golden Tree Laurelin), pl. glewair (in glewair**) (VT41:10) GOLD (COLOUR?) *mall (i vall), pl. mail (i mail) if there is a pl. Suggested Sindarin form of ”Noldorin” malt.
1) megil (i vegil), no distinct pl. form except with article (i megil). This is a borrowing from Quenya macil (VT45:32). 2) magol (i vagol), analogical pl. megyl (i megyl), coll. pl. maglath (though analogical ?magolath may also be possible). In ”Noldorin”, this was the native word for ”sword” (derived from primitive makla, as is Quenya macil); it is unclear whether Tolkien definitely replaced it with megil when he turned ”Noldorin” into Sindarin, or whether both words coexist in the language. 3) lang (cutlass), pl. leng.