Y is for Yielding Parry
A yielding or ceding parry is a parry executed against a flowing attack without separating the blades.
For example. You lunge and your opponent parries. As he counter attacks you remain in contact with his blade as you slide his foible into your forte and parry him in return. This is a move for point work (small-sword, foil, épée) and is a nice contrast to the sound of tick-tacking blades (if you were choreographing a fight…).