Definition of "signal flag" []

• A rectangular piece of fabric used as a signalling device (noun)

WordNet. Princeton University. 2010.

• "As the British destroyers astern of Tipperary swerved to avoid the blazing wreck, they used their 4-inch guns to rake the superstructures of their massive opponents, hitting bridges, searchlight stations, and signal flag positions."
• "Once the signal flag commanding a turn was hauled down at 4: 41 p.m. and Lion actually began to turn, no one on the flagship’s bridge noticed that the 5th Battle Squadron continued racing south."
• "These signposts are basically proteins on the surface of cells, and they wave like flags in the wind during development so that when the myelinated axon gets there it’s like a signal flag telling the axon which direction to head in to connect with the right muscle and, conversely, which direction to avoid."