Trisexuality has had several definitions, both of them have been inaccurate and...kinda wrong. The first definition was "an alternate name to pansexual", which is bad since it implies there are only 3 genders. Then there's "attraction to men, women, and animals" which is wrong for...obvious reasons. The new definition of trisexual
is attraction to any 3 genders. The flag was changed because the previous flag followed the definition of "an alternate name to pansexual". Trisexuality falls under the polysexuality/multisexuality umbrella alongside quadsexuality, bisexuality and polysexuality itself.