reptilian

adj

1. Of or relating to the members of the class Reptilia (reptiles).

   “The Mesozoic represents that time on Earth when life flourished, but when such life was primarily reptilian, before the Age of Mammals.”

2. Reptilelike.

   “It is filled with blazing fires and half-human, half-animal beasts, with spiked reptilian tails.”

3. (figuratively)Unthinking, low, base, contemptible.
4. (figuratively)Cold-blooded, treacherous, unavoidably selfish and hostile.

noun

1. A reptilian animal: a reptile.
2. (figuratively)A reptilian person, especially (ethnic slur) a Jew.
3. 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.”

   “Such powerful human families would descend upon the reptilians themselves and they would be willing to do just anything to retain their power.”

   “The reptilians are the creation of the Carians.”

   “Reptilians generally are envisioned as half snake, half human, and they are thought to have come from the Alpha Draconian star system.”