A crossword is a word puzzle, originating on Earth, which normally takes the form of a square or rectangular grid of black and white squares. The goal is to fill the white squares with letters, forming words or phrases, by solving clues which lead to the answers.
Colonel Jack O'Neill is quite fond of crossword puzzles. He is, however, not very good at them—often inserting incorrect answers and asking other people, such as Dr. Daniel Jackson, for assistance. In 2004 after using an Ancient Repository of knowledge, O'Neill inserted clues vital to finding the Lost City of the Ancients in a crossword puzzle—for thirteen across Jack wrote "Taonas" (sphere) and for eight down he wrote "Proclarush" (label). However, he also wrote "Uma Thurman" in response to the clue "celestial body" and "fat" as the atomic weight of Boron. (SG1: "Lost City, Part 1")