What is the definition or description of: well child visit?

It's a checkup: Well child visits are periodic scheduled visits at the doctor that includes appropriate for age screenings, anticipatory guidance, and a physical exam.

A check up: A well child visit is when you take you child to the pediatrician for his check up and shots. Pediatricians evaluate the growth and development of the baby in the areas of motor skills, language and social skills. They also check the nutritional status via height and weight checks, measure head size on the little ones and BP on the older ones.