half-mast noun 4verb 1forms 3 noun4 •The lowered position, half the height of a mast, at which a flag is flown when mourning, especially expressing respect for the deceased.Any other UK national flags flown alongside the Union Flag when it is at half-mast should also be at half-mast. — 2016 •The lowered position of anything. •(informal) An unfashionably short length of a pair of trousers. •(informal, euphemistic) The state of having a partially erect penis.Finally, he was at half-mast, hanging out over the toilet seat, barely erect. — 2009 verb1 •To fly a flag in this position. formshalf-masted · half-masting · half-masts