|body mass index|
|BMI an index used to indicate whether a person is over- or underweight. It is obtained by dividing a person's weight in kilograms by the square of their height in metres. An index of 20--25 is normal|
body mass index n.
A measurement of the relative percentages of fat and muscle mass in the human body, in which mass in kilograms is divided by height in meters squared and the result used as an index of obesity.