When one asks another verbal mammal to spell iCup, they are attempting to humiliate said animal by getting them to speak the words: "I see you pee", to which

Marginalized Orientations, Gender identities, And Intersex. it’s meant to be an all inclusive umbrella term for asexuals, homosexuals, multisexuals, trans people, and intersex people. Alternative to LGBTQIAP+
Alternative to MOGII, easier to pronounce.

Something you can do on your naive siblings or friends in public to embarrass them.

It started out as a way of Playground trickery and now has spiraled to an ironic meme. With the meme often containing images of a person with lens flares for eyes and the image being saturated beyond belief with the caption "Spell Icup".