Fed critics like that definition because it lets them more easily paint the fed in a bad light. They claim the fed is crazy because prices never fall. I think that's disingenuous because of the improper definition of 'transient'.

Will inflation be transitory? Probably yes, if you use the first definition. I don't think there has been a situation in modern history where prices in America have backed off significantly. Prices are sticky, especially when labor shortages combine with inflationary pressures to drive up wages and therefore the costs of production. I suppose you could take a few hits off Cathy Woods' pipe and claim robots will take all of our jobs and send us into a deflationary spiral next year, but I think that's likely several years away at best.