According to Diogenes Laërtius, when Plato gave the tongue-in-cheek definition of man as "featherless bipeds," Diogenes plucked a chicken and brought it into Plato's Academy, saying, "Behold! I've brought you a man," and so the Academy added "with broad flat nails" to the definition.

What is featherless biped?

Noun. featherless biped (plural featherless bipeds) (idiomatic, usually humorous) A human being.

What is the meaning of man is an upright featherless biped with broad flat nails?

Plato defined man as “featherless bipeds”. ... I've brought you a man.” After this incident, Plato added “with broad flat nails” to his definition of man. As technology diminishes the evidence of human labor, such labor becomes subsequently devalued.