Which shape is defined as a four-sided plane figure with four right angles?

A shape that is defined as a four-sided plane figure with four right angles is known as a rectangle. This definition specifically highlights the essential characteristics of a rectangle: it has four sides (also referred to as a quadrilateral) and each interior angle measures 90 degrees, which are the right angles.

Additionally, the rectangle is a special type of quadrilateral that also encompasses squares as a subset, where all sides are of equal length in addition to having right angles. The defining property of the four right angles differentiates rectangles from other quadrilaterals, ensuring their classification as rectangles specifically.

Other options do not fit this definition; for instance, a circle does not have sides or angles because it is a round shape, while a trapezoid typically has only one pair of parallel sides and does not require all angles to be right angles. A triangle, being a three-sided figure, also cannot meet the criteria of having four sides and right angles.

Thus, the rectangle is the correct answer for a four-sided figure defined by four right angles.