We don't have synonyms for gainers yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are gainer, gaiters and gaines.
(n) :
(diving, gymnastics, slang) A diving or gymnastics maneuver, from a high diving board or platform, involving a simultaneous inversion and rotation.
(n) :
(diving, gymnastics, slang) A diving or gymnastics maneuver, from a high diving board or platform, involving a simultaneous inversion and rotation.