Lipograms are poems, paragraphs or longer writings where one or more letters are not used, The most common lipograms omit the letter "e", the most commonly used letter in English.
Here are some well known poems rewritten as lipograms.
The best known lipogram, which omits the letter "E", is the 50,000 word novel Gadsby, written by Ernest Vincent Wright in 1939. . Wright taped down the "E" on his keyboard so that he wouldn't use it by mistake. It surprised me to find it online. I've read about 1/4 of it (it's best read in small segments). It's pretty bizarre, frequently funny, and quite an achievement.