I've noticed a change in the meaning of "pistol". Used to be, pistol meant the same as handgun, and came in two flavors, revolvers and automatic pistols. Recent usage in the trade seems to use "pistol" to mean "automatic pistol" and not revolver. Handgun is now the generic word that includes revolvers and automatic pistols.
This change has filtered thru to the dictionary. A great big 1967 dictionary defines pistol to be the same as handgun, a firearm designed to be fired with one hand. A newer 1997 dictionary drops the "fired with one hand" bit and defines pistol as a handgun with a single chamber, which rules out revolvers.
Part of the change comes from Charles Weaver, who taught us all the two hand hold for combat shooting. Weaver had something. I was taught to shoot single handed. Only after I switched over to Weaver's two hand grip did I win an Air Force sharpshooter ribbon. And if you watch TV, the cops now always grab their guns with two hands, which kinda makes the "designed to be fired with one hand" definition passe.