Simstim is short for simulated stimuli. A term used(coined?) by William Gibson in his works. Simstim is basically virtual reality. The main difference between simstim and the concepts of virtual reality is that simstim actually allows you to have feelings "run" in your head. Simstim devices can record the physical, emotional, and sensual states happening and then replay it back. In William Gibson's works, many characters use simstim to escape from their own dreary lives. With simstim "videos" resembling music videos at times, and placing the user within their favorite celebrity's head.

Want to feel someone else's emotions, simstim can give you that.

Want to know what it feels like in the day of someone of the opposite sex, simstim can give you that.

Want to know what orgasm feels like for the opposite sex, or even for just someone else, simstim does it.

Simstim is used in William Gibson's Cyberspace trilogy: Neuromancer, Count Zero, and Mona Lisa Overdrive. As well as many of his stories, such as Fragments of a Hologram Rose which uses it as a main point.

The device in Strange Days could also be considered a simstim device. The machine was able to record the events and feelings that the man was feeling, and then replay it back.

One could also trace back at least some of the ideas of simstim to Phillip K. Dick's works, particularly Do Androids Dream of Electric Sheep? The mood machine in the book is an identifiable predecessor to simstim. This machine allowed one to program in a number, and each number referred to an emotion and different degrees of it. This allowed a wide access to feelings that a person might not normally have.

Other similiar concepts can be found in Masamune Shirow's Ghost in the Shell, known as simex, and Shadowrun's simsense.