Which word refers to something that stimulates sexual desires?

The term that refers to something that stimulates sexual desires is "salacious." This word is often used to describe material, discussions, or themes that are intended to provoke erotic interest or are characterized by an overtly sexual nature. The context in which "salacious" is used typically connotes a certain level of immodesty or inappropriate allure, making it distinctly associated with sexual arousal and desire.

The other choices illustrate different meanings: “somniferous” relates to inducing sleep, “redress” refers to making amends or correcting a wrong, and “sagacious” describes someone who is wise or has keen insight. Each of these words carries its own specific connotation and does not have any direct relation to the stimulation of sexual desire, highlighting why "salacious" is the right choice for this question.