A step sequence prescribed by an ISU diagram and skated to set music, rhythm and tempo. Because everything is fixed, your technique gets judged rather than your ideas.
Pattern dances are the syllabus of ice dance rather than its showpiece — and that is exactly their value. Because the steps, the music and the pattern are all fixed, edge quality and timing can be judged entirely independently of choreographic ideas. Seven criteria are scored: accuracy to the diagram, placement on the ice, skating skills, timing, style, unison and presentation. The typical mistake is playing for elegance instead of hitting the line exactly — looking good does not pay here, but having your blade in the prescribed place at the right beat does. So drill a new pattern dance without music first, counting it out. How central they remain shows in the rulebook itself: in the novice category, two different pattern dances replace the rhythm dance.