Wiktionary
abdominal reflex
n. (context medical English) An involuntary contraction of the abdominal wall with stimulus of the covering epidermis.
Wikipedia
Abdominal reflex
An abdominal reflex is a superficial neurological reflex stimulated by stroking of the abdomen around the umbilicus. It can be helpful in determining the level of lesion in a neurology case. Being a superficial reflex, it is polysynaptic.