square
A 3 sided shape is a triangle. A 4 sided shape could be a square or rectangle.
A quadrilateral.
quadrangle
Quadrilateral
Get any 4 sided shape and vary all the sides to different lenghts and make it look weird-there you go an irregular 4 sided shape.
Tetrahedron
a square
square
Quadrilaterals
sqare
There is no specific name for such a shape.
It is a quadrilateral with no special name.