The term 'telegrammic period' refers to a period of time in which telegrams were the primary form of communication. It was a period of rapid technological advancement, as telegrams allowed for messages to be sent quickly and efficiently over long distances. The term is often used to refer to the late 19th century and early 20th century, when telegrams were the most popular form of communication. The crossword solution for this term is 'STOP', which is the signal used to indicate the end of a telegram.