Flag1  —n. 1 a usu. Oblong or square piece of cloth, attachable by one edge to a pole or rope as a country's emblem or standard, a signal, etc. B small toy etc. Resembling a flag. 2 adjustable strip of metal etc. Indicating a taxi's availability for hire. —v. (-gg-) 1 a grow tired; lag (was soon flagging). B hang down; droop. 2 mark out with or as if with a flag or flags. 3 (often foll. By that) inform or communicate by flag-signals.  flag down signal to stop. [origin unknown]