Whenever I'm playing Omega Ruby and a Pokémon uses Fire Blast, it shows some sort of symbol being blasted at the opponent. Does this symbol mean anything in Japanese/another language, or is it just there to look cool?
Its animation is based on the Daimonji of the Japanese festival Gozan no Okuribi, where a large bonfire is lit in the shape of the character 大 (meaning "big" or "great").
Source: http://bulbapedia.bulbagarden.net/wiki/Fire_Blast_(move)#Trivia Extra reading: http://en.wikipedia.org/wiki/Gozan_no_Okuribi
Yep!
Its animation is based on the Daimonji of the Japanese festival Gozan no Okuribi, where a large bonfire is lit in the shape of the character 大 (meaning "big" or "great"). Source: Bulbapedia page for Fire Blast