A blue flag with a white square in the centre, raised by a ship about to leave port.
开船旗（表示船只即将离港的信号旗，蓝色底，中间有白色方块）
Example sentencesExamples
Manoeuvring my newly-articulated bike as gingerly as a first-time driver, I moved off with the flag on the back of the trailer fluttering like a Blue Peter.
I was just about to raise the Blue Peter then and go without you, mate!
The captain, believing the seaport to still be in Union hands, raised a "blue peter" flag, which was the international marine signal to take aboard a pilot.
Whilst we were still on shore in Conquerno the Colonel, who was still on board, raised the ‘Blue Peter’ to the mast head.
Definition of Blue Peter in US English:
Blue Peter
nounˈˌblo͞o ˈpēdərˈˌblu ˈpidər
A blue flag with a white square in the center, raised by a ship about to leave port.
开船旗（表示船只即将离港的信号旗，蓝色底，中间有白色方块）
Example sentencesExamples
I was just about to raise the Blue Peter then and go without you, mate!
Manoeuvring my newly-articulated bike as gingerly as a first-time driver, I moved off with the flag on the back of the trailer fluttering like a Blue Peter.
The captain, believing the seaport to still be in Union hands, raised a "blue peter" flag, which was the international marine signal to take aboard a pilot.
Whilst we were still on shore in Conquerno the Colonel, who was still on board, raised the ‘Blue Peter’ to the mast head.