body mass index

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A measurement of the relative percentages of fat and muscle mass in the human body, in which weight in kilograms is divided by height in meters squared and the result used as an index of obesity.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun a statistical measure of the weight of a person scaled according to height, used to estimate if a person is underweight or overweight. BMI units are defined as ≈ .

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a measure of someone's weight in relation to height; to calculate one's BMI, multiply one's weight in pounds and divide that by the square of one's height in inches; overweight is a BMI greater than 25; obese is a BMI greater than 30