In the United States, yes its very definition is a general irregular quadrilateral. However, outside the U.S., its the same thing as a trapezoid and there are regular and irregular trapezoids.
A trapezium is considered to be a regular shape. The trapezium is referred to as a regular polygon which has all sides equal.
A trapezium is not a regular shape although it is a 4 sided quadrilateral.
It is irregular.
A trapezium cannot be regular, so the question concerns something that cannot exist.
A parallelogram, a rhombus, kites, arrowheads, trapezium and irregular quadrilaterals. However, some kites, arrowheads, trapezium and irregular quadrilaterals can have one (or more) right angles.
Pentagons can be regular or irregular.
A pentagon can be regular or irregular.
Kite: 0Trapezium: 1 pairRegular hexagon: 3 pairsIrregular quadrilateral: 0, 1 or 2 pairs.Kite: noneTrapezium: one pairRegular hexagon : three pairsIrregular quadrilateral: none, one or two pairs.