A double-action revolver is a semi-automatic weapon.
One trigger pull, one shot, ready to fire again immediately.
Semi-automatic firearms have also been commonly referred to as "self-loading" firearms - when a cartridge is fired, part of the energy from that cartridge is used to load a new cartridge in the chamber (i.e., the firearm essentially reloads itself). That is not true of most revolvers; the energy for rotating the cylinder generally comes from the operator, not the cartridge. Historically, there has been a similar distinction between "automatic" weapons and hand-cranked rapid-fire weapons like the Gatling gun.
None of which should suggest to anyone with even a trace of common sense, that the Democrats won't ban revolvers as soon as they get a chance...