Intermittent vasospasm of the arterioles of the distal limbs (fingertips and toes) after exposure to cold. Named after Maurice Raynaud, a French physician who first describe it in 1862.
Idiopathic Raynaud's is called Raynaud's disease, while Raynaud's secondary to an underlying cause is Raynaud's phenomenon.
Treatment: keep the affected limb warm.