Hardcore sex with my step sister.. she suck my dick.. I love my step sister.. What is the main description of sex? Sex refers to a set of biological attributes in humans It is primarily associated with physical and physiological features including chromosomes, gene expression, hormone levels and function. Sex is anything that is physically, mentally, and emotionally arousing, pleasurable, and leads to satisfaction. This definition does not include penis, vagina, intercourse, or orgasm, although these can be part of sex but are not required.