Passé is a classical ballet term meaning “passed.” It refers to the movement when a dancer goes through a retiré position, which is when one leg is bent so it looks like a triangle with the foot placed near the other leg’s knee.
In ballet class, passé is often used instead of retiré to describe the position of a leg. For example, a teacher may say “Higher passés in your pirouettes ladies!” Both terms are accepted and understood to basically mean the same thing.
As the technical and physical abilities of dancers have improved over the years, so have the precision of positions, with passé being one of the major improvements over the years. Many expert and professional ballet dancers from the mid-50s and even into the 80s would have a “low passé” where the angle or direction of the knee with the top of the thigh would be pointing downward toward the ground instead of being held at 90 degrees as is expected today of advanced ballet students to professionals.