1. A stimulant of some kind; that which quickly imparts energy and alertness. I find that yerba mate tea is a much better pepper-upper than coffee—it gives you the same boost, without making you feel jittery or on-edge.

2. Something that increases enthusiasm, optimism, or eagerness. I hate these public speakers they bring in—they're meant to be pepper-uppers, but they just come across as totally phony to me.