LogFAQs > #888793110

Not that Wiki is the best source but:

A semi-automatic pistol is a type of pistol that is semiautomatic, meaning it uses the energy of the fired cartridge to cycle the action of the firearm and advance the next available cartridge into position for firing. One cartridge is fired each time the trigger of a semi-automatic pistol is pulled; the pistol's "disconnector" ensures this behavior.

Additional terms sometimes used as synonyms for a semi-automatic pistol are automatic pistol, self-loading pistol, autopistol, and autoloading pistol.

A semi-automatic pistol harnesses the energy of one shot to reload the chamber for the next. After a round is fired, the spent casing is ejected and a new round from the magazine is loaded into the chamber, allowing another shot to be fired as soon as the trigger is pulled again. Most pistols use recoil operation to do this, but some pistols use blowback or gas operation.

Revolvers simply rotate a center chamber by having it connected to the trigger pull. There is nothing automated or "semi-automated" involving feeding, ejecting, extracting or anything else.