The story
From boat + sex, referencing the scene's setting. The term was coined before season 7 aired due to plot leaks.
Etymology from Wiktionary, CC BY-SA 4.0.
boatsex
Today it means: The Jonerys sex scene in the season 7 finale of Game of Thrones, set in the cabin of a ship on which Daenerys and Jon are sailing together. Full definition →