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ἀνυποστρεπτί

From LSJ

Γελᾷ δ' ὁ μωρός, κἄν τι μὴ γέλοιον ᾖ → The fool laughs even when there's nothing to laugh at

Menander

Spanish (DGE)

adv. sin volver la cabeza βάδιζε Pythag. en Phlp.in de An.116.32.