Gigaflare Sword (ギガフレアソード, Giga Furea Sōdo?) is a recurring ability in the Final Fantasy series, used exclusively by Vayne Carudas Solidor. It calls back to Bahamut's similarly named "Megaflare" ability.
Vayne's final boss form uses parts of Sky Fortress Bahamut for his transformation, and thus his attacks recall the summon's attacks in allusion. Bahamut is a recurring dragon king character and summon in the series, whose signature attack is Megaflare.
Giga is a unit prefix in the metric system denoting a factor of a (short-form) billion (109 or 1,000,000,000). It has the symbol G.
flare is a pyrotechnical phenomenon that produces intense amounts of heat and energy that does not result in an explosion (an immediate release of energy).A