From The Simpsons, Episode CABF12, New Kids on the Blecch:

Lisa discovers Lieutenant L.T. Smash is recruiting for the Navy using subliminal messages.

Lisa: But you've got recruiting ads on TV - why do you need subliminal messages?
Lt. Smash: It's a three-pronged attack. Subliminal, liminal and superliminal.
Lisa: "Supraliminal"?
Lt. Smash: I'll show you. {yells out the window to Lenny and Carl} Hey you, join the navy!
Carl: Ahh, yeah alright.
Lenny: I'm in!

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Superliminal isn't technically a word, but the informative liminal node speculates on what it might mean. Supraliminal describes a stimulus that registers within the conscious, unlike a subliminal stimulus. Following this progression, superliminal, as the Lieutenant would define it, might be a conscious stimulus that is so strong as to be irresistible.