Dictionary:

quadrat

  (kwŏd'rət, -răt')

1. Printing. A piece of type metal lower than the raised typeface, used for filling spaces and blank lines. Also called quad.
2. Ecology. Any of a group of small, usually rectangular plots of land arranged for close study of the distribution of plants or animals in an area.

[Middle English, a square geometric instrument, rectangular area. See quadrate.]

A small, usually square, frame used in sampling, notably in biogeography and ecology. Quadrats are placed systematically or at random over the area to be studied and the vegetation occurring within the quadrat is recorded.