Meaning of affirmative flag

affirm'ative flag'

Pronunciation: [key]
— Naut. Naut.
  1. a flag having five horizontal stripes, blue, white, red, white, and blue, from top to bottom, signifying “yes”: letter C in the International Code of Signals.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.