Skyn is one of the few words evoking nostalgia for life as a synth. At the time, of course, skyn was a nightmare, a cheap, low quality attempt at human sensation that trapped early synthmorphs in numb bodies. Synthmorph sensoriums have improved to and past the human level, and only the early-adopters remember.
Skyn is a thin, flexible and clingy sheeting similar to plastic wrap. The thin material contains layers of simple sensors for heat, pressure and relative position. In this way it simulated the perceptions of human skin, with its knowledge of relative position acting as proprioception. Contemporary synthmorphs, even cases, have all these senses built in; skyn is only occasionally still used as an area sensor.
Skyn is sold by the square meter [Trivial]
Skyn senses pressure, heat and relative position. It is at its best as good as the sense of a baseline human, but degrades rapidly.