Something scintillating is flashing briefly and sharply with light. Scintillating conversations are smart and captivating.
To be scintillating is to be sharp. Things that are scintillating are exciting: they grab your attention with sparkles, flashes of light, or sheer brilliance. Most often, we talk about scintillating conversations and speakers. If you say someone is scintillating, then they are clever — people want to listen to them. This is a word often used sarcastically. If someone is boring, you might say "Well, that was scintillating," while rolling your eyes.