A blue signal flag with a white rectangle in the centre, signifying "P". When flown alone, indicates that a ship is ready to sail, requiring all crew members and passengers to return on board
We lay out in the stream for another whole day, with the Blue Peter flying, to show that we were ready for sea, and to summon any passengers who might yet remain on shore. — W.H.G. Kingston, Peter the Whaler, 1851.
a blue flag with a white square in the center indicates that the vessel is ready to sail
{i} blue signal flag that has a white square in its middle (vessels use it to signal that they are ready to sail)
A blue flag with a white square in the center, flown to signal that a ship is ready to sail. a children's programme that has been on British television since the late 1950s. It is known for encouraging children to collect money or things for people who are poor or sick, and for showing them how to do and make useful things