An acrostic is a poetic technique in which a word—any word—is written vertically down the page. This arrangement allows words and phrases to flow from each letter of the vertical word. 

In this example, the author explores a new technique using the word "PRESSURE." Starting with the letter "P," he chooses the word "Please." The next line begins with the letter "R," which rhymes with "Please," and the second word in that line must also start with "R." This pattern continues, with each line increasing in length until the final line, where the last word must rhyme with the last word of the previous line.