More grue than you knew.
Grue is defined by Dictionary.com as a shudder, or to shudder:*
grue(ɡruː)
n
1.a shiver or shudder; a creeping of the flesh
vb
2.to shiver or shudder
3.to feel strong aversion
Wiktionary has more to say on the origin of the word, the difference between grue and bleen and how butchers sometimes get covered in grue.
Grue is horror, or that which causes it. It is also a topic of philosophical study: something that at first appears green, but turns (or turns out to be) blue. Interestingly, it seems that in some languages, like Welsh, there is no distinction between green and blue. There we have grue.
Grue as a surname is rumored to be of French origin, with a possible meaning of thin man. I have also heard of McGrues. They don’t come in a happy meal.
Oh, yeah. And there was this game Zork. In this text adventure, grue lurk in the absolute dark awaiting their favorite food source: unwary adventurers. If you are not familiar with text adventures, you may not want to be. They are infuriating games invented by techno-wizards with a lone purpose to ensure keyboard sales. Zork can be played online, or downloaded for pc or mac. Also check your app store on mobile.
Occasional Grue 