/,ʌndə'weɪt; `ʌndɚ`wet/
adj below the usual, legal or stated weight 低于一般重量的; 未达标准或规定之重量的; 重量不足的
*You are only slightly underweight for (ie in relation to) your height. 按你的身高来说, 你体重仅稍轻一点儿.
* The coal is six pounds underweight/underweight by six pounds. 这些煤的重量少了六磅. =>Usage at thin 用法见thin. Cf 参看 overweight.

adj
weighing less than is expected or usual
≠ overweight
　Women who smoke risk giving birth to underweight babies.