Push Sweep is one of the guard sweeps described in Brazilian Jiu-Jitsu, Theory and Technique by Renzo Gracie and Royler Gracie. It is also demonstrated in The Essence Of Judo by one of Kyuzo Mifune's student, and it is an un-named technique described in The Canon Of Judo.
The main characteristic of the Push Sweep is the push with tori's foot of uke's knee out from under uke when tori has uke in his open guard.