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• a  having a projecting lower jaw

• Her jaw is on the prognathous side.
• A florid, prognathous man with a taste for flashy clothes, he was the only Pittsburgh mayor to serve two successive terms under the city's present charter (which dates from 1903.
• When commanded, the robot lowered its arm, raised the other, lowered it, turned its head from side to side, opened and closed its prognathous jaw, sat down.

• prognathic
• hypognathous

• opisthognathous