Head up definition, the upper part of the body in humans, joined to the trunk by the neck, containing the brain, eyes, ears, nose, and mouth. See more. Heads - up definition, quick to grasp a situation and take advantage of opportunities; alert; resourceful. See more. Several of the meanings of this phrase allude to holding one's head up high and concentrating on what one is doing. Residents of the USA will have come. Head case "eccentric or insane person" is from For, as they passed through Tilford they had seen horse and man walking side by side and head by head up the manor-house lane. Judy was chosen to head up the department. New Words uncanny valley noun July 10, The Macmillan Dictionary blog explores English as it is spoken around the world today. Informal Information or notification: A whirlwind romance has quite turned his head.