A parallelogram with sides of equal length (equilateral) is called a rhombus but not a rhomboid.

A parallelogram with right angled corners is a rectangle but not a rhomboid.

And let quadrilaterals other than these be called trapezia.Euclid never used the definition of rhomboid again and introduced the word parallelogram in Proposition 34 of Book I; "In parallelogrammic areas the opposite sides and angles are equal to one another, and the diameter bisects the areas."

[1] In a type of arthritis called pseudogout, crystals of calcium pyrophosphate dihydrate accumulate in the joint, causing inflammation.

Aspiration of the joint fluid reveals rhomboid-shaped crystals under a microscope.