I call it fainting, because that is what it is called 99.9 percent of the time in the games. Not only is referred as such, but that is actually what is happening - the Pokémon temporarily comatoses and is woken up in time for the next battle (if healed). The only time that the word "dying" is used is either due to an error in translation or a legit death that more than likely occurred outside of battle due to natural ailments (e.g., Lavendar Town). Goddess forbid a Pokémon actually "dies" in battle...
...just saying.