A synthetic call option that is established by combining a short put and a short stock or futures.

Synthetic short call = short put + short underlying stock

This position is practically equivalent to a short call: both are a limited gain strategy with unlimited potential losses. The short stock position loses when the underlying stock moves up. The potential profit results from the short put, which could be realized in full only if the option expired out-of-the money (i.e., it ended up worthless at expiration date).