reptilian

Etymology

From reptile + -ian, replacing earlier reptilious and adjectival reptile.

adj

1. (zoology) Of or relating to the members of the class Reptilia.
   The Mesozoic represents that time on Earth when life flourished, but when such life was primarily reptilian, before the Age of Mammals. 2012, Chinle Miller, In Mesozoic Lands: The Mesozoic Geology of Arches and Canyonlands National Parks, Kindle edition
2. Reptilelike.
3. (figurative) Unthinking, low, base, contemptible.
4. (figurative) Cold-blooded, treacherous, unavoidably selfish and hostile.

noun

1. A reptilian animal: a reptile.
2. (figurative) A reptilian person, especially (ethnic slur) a Jew.
3. (science fiction) A reptilian alien, especially (ufology, often capitalized) of a shapeshifting race alleged to secretly control the world.
   More evolved than the Grays or Reptilians, the Humanoids seem to feel some sort of kinship with humans and are likely to be kind.[…] Some researchers believe the Grays are merely preparing the way for a full-scale invasion of Reptilian aliens. 2001, Caroline Tiger, The UFO Hunter’s Handbook: A Field Guide to the Paranormal, pages 62–63
   Such powerful human families would descend upon the reptilians themselves and they would be willing to do just anything to retain their power. 2010, Chico Penteado, Talking to the Reptilians-A Report from Brazil, page 11
   The reptilians are the creation of the Carians. 2011, Collin Robert Bowling, A New Order of the Ages
   Reptilians generally are envisioned as half snake, half human, and they are thought to have come from the Alpha Draconian star system. 2015, Marty Crump, Eye of Newt and Toe of Frog, Adder's Fork and Lizard's Leg