From Team Fortress Wiki

Voice Responses are contextually triggered lines that play after the player has achieved something, for instance killing a certain amount of enemies with a Primary or Melee Weapon, or the player has triggered something, like being set on fire. The Pyro doesn't have many voice responses, but all of them are listed below (excluding Voice Commands).

Taunt-related responses

All voice lines associated with a player-initiated taunt are located in the Pyro taunts page along with a description of the animation.

Kill-related responses

After Killing More than 1 Enemy in 20 Seconds with a Primary Weapon "Ow dow how dow." (Possibly "I'm on fire now," or "I don't think so" or "Not in my house" or "Oh well hi there!")

Event-related responses

Stalemate "Mmmrpgh crpyha drghya!" (Possibly "Can't believe that someone would do that," or "Now I need a towel.")

Under the effects of an ÜberCharge Mumbling gibberish (Possibly "Oh really? I'm paying myself after that!" or "You idiots aren't the only ones I'll burn today!" or even "You idiots aren't the only ones I've burned today!")

Long laugh

Objective-related responses

After Capturing Intelligence "Mmmphya harrgh mrgha hrghgph!" (Possibly "I don't know why I've got to do everything." or "I gotta do the job of everyone!")

Setup

Previous round was a win "Heh dum dummad" (Possibly "We're gonna kill em all!")

The 7th spell line of the Pyro is unheard in the game, while some lines are used twice. RED and BLU Pyro have the same lines.