The Alien Nightmare is an induced dream state when one is given a sleep aid such as Advil PM, Tylenol PM, or NyQuil and a horror / thriller movie (i.e. Alien 3) is turned on at full volume thus inducing a literal Alien Nightmare or a horrific dream that the now sleeping person is incapable of waking from.
My girlfriend was pissing me off so I fed her NyQuil and put her in an alien nightmare.
by Mr. M.L.G. MLG June 30, 2009