This is a game to play with other people or, in extremis, with yourself. Choose a category—birds, say, or colours. Then go through the alphabet and try to name an example starting with each letter. The game is collaborative rather than competitive—the pleasure lies in getting as close as possible to a full alphabetical set.
The categories are usually dictated by the interests and obsessions of the participants. With Pete, I play footballers, scientists and mathematical terms. With my brother, fictional detectives, methods of murder and world-historical figures. With my mother, operas, novelists and words that start and end with the same letter. Sometimes the category chosen proves too restrictive and a second category is added. This was the origin of “figure of speech or rude word,” a memorable and entertaining round.