1. A condition of weariness or debility; fatigue.
2. A condition characterized by lack of interest, energy, or spirit; languor.
“Lassitude” is a great word for those “fade-to-black” scenes, as below, to describe the sensation as someone is drugged or otherwise lulled to sleep. It’s also a word well-suited to describe the torpor of illness.
Etymologically, “lassitude” comes directly from French, which in turn comes from the Latin lassitudo (faintness, weariness) and lassus (faint, weary).
Thorne did as Dr. Morgan directed, and found that he was looking into a mirror painted with alternate circles of red and black. The doctor touched a button and the mirror began to rotate slowly. Morgan’s voice came to him, “Now think of that distant world, far off in time and space. Think of it beckoning you.”
Thorne obeyed, his eyes fixed on the mirror. He began to feel drowsy, a pleasant lassitude stealing over him. The doctor’s voice faded…
– Otis Adelbert Kline, The Swordsman of Mars (1933)