Lantern Test Share definition Flag Nurse slang; it means to shine a pen light in a patient's mouth and see their eyes light up (i.e., they have no brain.) She thought Smucker's could be used as contraceptive jelly. I think she'd fail the lantern test. Lantern Test by Nurse Whitney June 1, 2013 0 0 Get merch Get the Lantern Test mug. Buy Now — $32.95 See more merch