Occurs when your female partner is giving you a blowjob and then you cum in her mouth. Superbly she goes to swallow your load when you jam your cock in farther causing her to choke. This movement naturally re-routes your discharge through and out her nose creating the "Hangin Brain".
Due to Sara's superb oral efforts, I gave her a little extra. She smiled up at me with surprise exposing her new hangin brain.