|Italian||cavare (verb) cavatione (noun)|
To release your blade from constraint or after it has been gained. Generally performed by drawing a 'U' shape with your point underneath your opponent's sword that takes your point from one side of their sword to the other; this is known in Italian as cavare sotto.
This action can also be performed over-top by drawing an upside down 'V' shape (maintaining the position of the guard and withdrawing the point vertically using a rotation of the wrist and withdrawal of the forearm) that moves your point over their tip to the other side; this is known in Italian is cavare sopra.
When performing a disengage, it is best to move from the constrained position to one where you in turn constrain your opponent.
Capo Ferro states that when performing a disengage underneath the blade, move forward, when performing one over-top, move back. 
At Academie Duello, the disengage is generally taught to always be done with a retreat.