Final answer:
The Babinski sign is a reflex that involves dorsiflexion of the foot and splaying of the toes in response to the plantar reflex. It is abnormal in children older than 1 year and in adults and can be indicative of neurological conditions.
Step-by-step explanation:
The Babinski sign refers to the dorsiflexion of the foot with extension and splaying of the toes in response to the plantar reflex. This reflex is normally suppressed by corticospinal input from the cerebral cortex. In children older than 1 year and in adults, the presence of the Babinski sign is abnormal and can be an indication of certain neurological conditions, such as an upper motor neuron lesion.