Game concept
Extramarital Sex
The game also links it as sleeping with.
From the game's encyclopedia
If they are discovered, two characters engaged in extramarital sex will suffer consequences depending on their Faith's Doctrines.
• Each character will become known as either a Fornicator or an Adulterer, depending on their own marital status
• If a man and a woman sleep together, it may result in a Bastard pregnancy
• If the characters are of the same gender, consequences are determined by their Faith's Same-Sex Relations Doctrine
• Any sexually transmitted Diseases held by one character may infect the other
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Extramarital Sex is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "If they are discovered, two characters engaged in extramarital sex will suffer consequences depending on their Faith's Doctrines." The game also links it as sleeping with. Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/00_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.