means Insolence is rude, contemptuous disrespect — the kind of cheek that treats authority or another's dignity as beneath notice.

from From Latin insolentia, the noun behind insolens, meaning 'unaccustomed, immoderate, arrogant.' Break it down and it's in- ('not') plus solere ('to be accustomed') — so the insolent person is literally one who does not behave as is usual or fitting, someone unbound by the customs of deference. It traveled through Old French into English in the late medieval period, where its earlier sense of 'extravagant, over-the-top behavior' narrowed into the sharper modern flavor of bold disrespect.