| TRAPEZIUM | A quadrilateral with only one pair of sides parallel |
| TRAPEZIA | Quadrilaterals with only one pair of parallel sides (8) |
| TRAPEZOID | Quadrilateral with neither pair of sides parallel |
| TRAPEZIFORM | Having the shape of a quadrilateral with two parallel sides |
| RHOMBUS | A quadrilateral with sides of the same length (7) |
| KITE | In geometry, a quadrilateral with reflection symmetry across one of its diagonals (4) |
| SQUARE | A tool for determining a right angle; a cotton flower-bud; a quadrilateral; or, something four-sided, such as a cell in a crossword grid, a chocolate brownie, a formation of troops, a marketplace, a m |
| RECTANGULAR | Shaped as a quadrilateral with four right angles (11) |
| PARALLELOGRAM | Quadrilateral with opposite sides parallel |
| ODDNESS | Characteristic of one pair of diamonds among one pair of spades |
| DIAGONAL | A straight line running in a oblique direction between opposite, non-adjacent corners of a quadrilateral (8) |
| RHOMB | From Greek for "bull-roarer", "magic wheel" or "spinning top", a quadrilateral also called a diamond or a kite; or, a lozenge-shaped thing (5) |
| NEPAL | With symbols including the rhododendron and Himalayan monal, the only country that doesn't have a quadrilateral national flag (5) |
| RECTANGLE | Trace out, missing a corner, a quadrilateral (9) |
| PTOLEMYSTHEOREM | Math conjecture regarding a quadrilateral inscribed in a circle |
| SWIMMINGLY | Half of 8 women and one pair of males split one by one (10) |
| DICKENS | Great-granddaughter of "Boz" who penned One Pair of Hands, My Turn to Make the Tea, One of the Family and the Follyfoot series (7) |
| DIPTERA | Order of insects with one pair of wings |
| GAFF | Spar to which the upper edge of a quadrilateral fore-and-aft sail is attached (4) |
| AREA | Width times length for this in a quadrilateral (4) |
