Springing Line
Springing Line is an imaginary line joining the springing and points of either end.
Pringer
Pringer is the first voussoir at springing level; it is immediately adjacent to the skewback.
Arcade
Arcade is a row of arches supporting a wall above and being supported through piers.
Haunch
Haunch is the lower half portion of the arch among the skew-back and the crown or springer.