Rat Defense

The Rat Defense, English Rat is an irregular Queen's Pawn Game chess opening characterised by the initial moves:
The position can also arise from the move order 1.c4 d6 2.d4 e5.
Lisbon Gambit.
One notable variation of the English Rat is the Lisbon Gambit which arises from:
1.d4 d6 2.c4 e5 3. dxe5 Nc6, which usually continues 4. exd6 Bxd6 or (4...Qxd6).
Rat Defense, Small Center Defense.
There is also an irregular chess opening called the Rat Defense, Small Center Defense which can arise from multiple move orders:
References.
Bibliography