A shamelessly bold untruth/prevaricator.
Bare here means bold-faced or brazen, but one writer speculates that
barefaced, which dates from the late sixteenth century, originally meant “beardless,” a condition perhaps considered audacious in all but the youngest men. In any event, by the late seventeenth century it also meant bold and became attached to
lie in succeeding years. See also
naked truth.