Can you tell me more about an ailment called stealer artery?

Steal. Refers to diverting blood flow when talking about arteries and veins. Commonly seen is subclavian steal syndrome. Stenosis or occlusion of the subclavian artery decreases direct flow to the arm. Blood to the affected arm has to be supplied by the vertebral arteries. This increased flow can "steal" blood from the back of the brain and make the patient dizzy.