American Heritage Dictionary
(1)
Century Dictionary
(5)
GNU Webster's 1913
(2)
WordNet
(1)
Elsewhere on the web
Here is a DNA origami rectangle, and here are some tiles growing from it.— Paul Rothemund details DNA folding
Is it true that a rectangle is a square if it has four congruent sides.? en Español— Yahoo! Answers: Latest Questions
When you point to the rectangle, the AutoCorrect Options button appears.— Lockergnome
The Water Cube, combining all the symbolism of the equilateral rectangle -- the fundamental shape of the house inherent to Chinese tradition and mythology -- with the natural structure of soap bubbles translated into architectural form, has been hailed as the showpiece of the Beijing Olympics.— Fulldls.com
There are also three different shapes you can "play" as (horizontal rectangle, vertical rectangle, and square), which goes a long way to providing the game with some longevity.— Destructoid

American Heritage Dictionary (1)
Century Dictionary (1)
Bubble size: how much this word was used in a year
Bubble height: used more or less than expected, vs. all uses evenly distributed
You can expect to see this word about twice a month.