"1. increased mechanical irritability of the sensory nerves in tetany; the ulnar nerve is usually tested.
2. a sudden nipping of the nail of the index, middle, or ring finger produces flexion of the terminal phalanx of the thumb and of the second and third phalanges of some other finger." Quoted from this link - http://medical-dictionary.thefreedictionary.com/Hoffman's+sign
or
"Hoffmann's sign is often considered the upper limb equivalent of the Babinski's sign because it, like the Babinski sign, indicates upper motor neuron dysfunction" Quoted from this link - http://en.wikipedia.org/wiki/Hoffmann's_sign