Babinski reflex

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. An extension of the great toe, sometimes with fanning of the other toes, in response to stroking of the sole of the foot. It is a normal reflex in infants, but it is usually associated with a disturbance of the pyramidal tract in children and adults. Also called Babinski sign, Babinski's sign.

Wiktionary

1. n. medicine An abnormal plantar reflex in which the hallux moves upwards, indicative of motor neuron damage.

WordNet 3.0

1. n. extension upward of the toes when the sole of the foot is stroked firmly on the outer side from the heel to the front; normal in infants under the age of two years but a sign of brain or spinal cord injury in older persons