incest

noun

1. (uncountable, usually)Sexual relations between close relatives, especially immediate family members and sometimes first cousins, usually considered taboo.

   “Genetic problems caused by incest are thought to have plagued many royal families in the Middle Ages.”

   “For a structuralist like Edmund Leach, the structure is the meaning. Genesis, for example, is about incest taboos; all the rest is noise and mystification.”

   “He was only Craster's whelp, an abomination born of incest, not the son of the King-beyond-the-Wall.”

2. (broadly, uncountable, usually)Romantic relationships between close relatives, also widely taboo.

verb

1. (ambitransitive)To engage in incestuous sexual activities.

   “I do not want anyone to feel that my lesbianism is a result of being incested.”

   “Her erotic transference ultimately devolved into a revelation that she had been consistently incested by her brother”

   “[…] the most powerful of that bunch of immortal giants called Titans was Cronus, who “incested” with sister Rhea, who then birthed the Olympians (Zeus and his bunch) […]”