(nautical) 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.

(card games, intransitive) In whist, to play a blue peter.

A cathedral city and unitary authority in Cambridgeshire, England, United Kingdom. / A town in South Australia, Australia. / A town on the Great Ocean Road, Victoria, Australia.

(slang) The penis.

(UK, slang) A safe.

(most often used in the phrase peter out) To dwindle; to trail off; to diminish to nothing.

(card games, intransitive) Synonym of blue peter

(UK, prison slang) A prison cell.

(slang) A safecracker.

A fisherman. / A fishing boat with identical bow and stern.