On the theory that a poor node is better than no node at all...
A Mexican (or at least American-Mexican) dish consisting of a fried tortilla topped with beans and/or meat, lettuce, cheese and guacamole.
A Google search finds 99 results for tostaguac, but also finds 20 results for tostaquac, which is exactly the same thing. Many restaurants will also give you one of these if you ask for a chalupa.
Any native Mexicans want to chip in here?