reptilian UK /ɹɛpˈtɪliən/US /ɹɛpˈtɪljən/adjective 4noun 3forms 3 adjective4 •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. — 2012 •Reptilelike.It is filled with blazing fires and half-human, half-animal beasts, with spiked reptilian tails. — 1982 •(figurative) Unthinking, low, base, contemptible. •(figurative) Cold-blooded, treacherous, unavoidably selfish and hostile. noun3 •A reptilian animal: a reptile. •A reptilian alien, especially (ufology, often capitalized) of a shapeshifting race alleged to secretly control the world.Such powerful human families would descend upon the reptilians themselves and they would be willing to do just anything to retain their power. — 2010 •(figurative) A reptilian person, especially (ethnic slur) a Jew. formsreptilians · more reptilian · most reptilian