Is either タイダルウェーブ [tidal wave] or タイダルウェイブ [tidal wave] in Japanese.
Final Fantasy III
Target: all enemies, Element: Water, Power: 350
Use: when casting Leviath on Summoner
Effect: deals extreme water element damage to all enemies
Other: in the NES version dealt lightning element damage instead, as water element didn't exist in the game
Other: タイダルウェーブ in Japanese
Final Fantasy V
Effect: ?
Targets: 1
Usable: Stingray
Opera Omnia
Target: all enemies, Element: Water, Type: Magic
Level 1: Deals 500 BRV damage of Water element to all enemies
Level 20: Deals 2,500 BRV damage of Water element to all enemies
Level 30: Deals 4,000 BRV damage of Water element to all enemies
Additional effect: grants Water element to all party members
Other: 大海嘯 [daitsunami] or 'big tsunami' in Japanese, making this another ability from those listed on this page
Final Fantasy Tactics
Other: the ability used by the summon Leviathan
Other: タイダルウェイブ in Japanese
Category: Ability