TexasCHLforum.com

BATF has in their regulations a definition for "pistol" and for "revolver".

27 CFR 479.11 - Meaning of terms. Subpart B

Pistol. A weapon originally designed, made, and intended to fire a projectile (bullet) from one or more barrels when held in one hand, and having (a) a chamber(s) as an integral part(s) of, or permanently aligned with, the bore(s); and (b) a short stock designed to be gripped by one hand and at an angle to and extending below the line of the bore(s).

Revolver. A projectile weapon, of the pistol type, having a breechloading chambered cylinder so arranged that the cocking of the hammer or movement of the trigger rotates it and brings the next cartridge in line with the barrel for firing.

And TXDPS separates the two in only one place:

PC Subsection 46.01(12) "Armor-piercing ammunition" means handgun ammunition
that is designed primarily for the purpose of penetrating metal or body
armor and to be used principally in pistols and revolvers. (emphasis mine)

It is the only place where "pistol" is found and only the second place where "revolver" is found.