Cowardly, spineless.
Without a backbone; invertebrate.
Cold-blooded, treacherous, unavoidably selfish and hostile.
Reptilelike.
Unthinking, low, base, contemptible.
Of or relating to the members of the class Reptilia.
A reptilian person, especially (ethnic slur) a Jew.
A reptilian animal: a reptile.
A reptilian alien, especially (ufology, often capitalized) of a shapeshifting race purported to secretly control the world.