What is "failure to thrive"

n. 1 (&lit failure thrive English) 2 (context uncountable pediatrics English) Poor physical growth or level of weight, relative to one's age peers. 3 (context uncountable medicine chiefly geriatrics English) Abnormal weight loss, malaise. 4 (context countable medicine English) Instances of poor physical growth or of abnormal weight loss.

Failure to thrive (FTT), more recently known as faltering weight or weight faltering, is a term used in pediatric, adult as well as veterinary medicine (where it is also referred to as ill thrift), to indicate insufficient weight gain or inappropriate weight loss. When not more precisely defined, the term refers to pediatric patients. In children, it is usually defined in terms of weight, and can be evaluated either by a low weight for the child's age, or by a low rate of increase in the weight.