An adjective denoting something that is, or is closely related to a plot device. The phrase is used to make plot devices blatantly obvious for what they are, and thus can be considered to be of significance to humor that intentionally breaks the fourth wall.
John leapt into the vat of radioactive waste, which plot-devicedly gave him super powers instead of radiation poisoning.
The heel of Mary's shoe suddenly snapped, sending her to the floor and plot-devicedly allowing her to evade the killer's axe.
The staggering blow would have been fatal to any normal human, but plot-devicedly enough Jack was the last survivor of an ancient race and the magic in his blood kept him alive; though removing all conflict from the story in doing so.
A product which is of incredibly low quality compared to its nearest competitors, yet maintains a similar price. The term originated from the tendency of such product to utilize colorful flashing lights (possibly in alternating or multiple colors) as a selling point.
Have you seen those cheap-ish third party controllers? Nothing but disco lights, they don't even have all the right buttons!
I got a new mouse, but it went bad after like a month. Stupid disco lights.
Sure this flash drive doesn't have the storage space or the lifespan as that other brand, but it lights up in blue, red, and green! I need some DISCO LIGHTS!
Man, fuck quality, I'm gonna buy some disco lights!