a meaurement used to estimate body fat and classify persons as being underweight, overweight, or normal: it is calculated by dividing weight (in kilograms) by the square of height (in meters)
See body mass index in American Heritage Dictionary 4
noun Abbr. BMI
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.