Noun has 3 senses

• gainer(n = noun.person) weight gainer - a person who gains weight;

Derived form verb gain₉

• gainer(n = noun.person) - a person who gains (gains an advantage or gains profits); "she was clearly the gainer in that exchange"

Derived form verb gain₂, verb gain₃, verb gain₅, verb gain₈

• gainer(n = noun.act) full gainer - a dive in which the diver throws the feet forward to complete a full backward somersault and enters the water feet first and facing away from the diving board;