Subclavian steal: Subclavian steal is stealing of blood from the blood vessels of the brain by blood vessels of the upper limb. One of the blood vessels of the brain arises from the blood vessel to the upper limb (subclavian artery). When the subclavian artery is obstructed before the origin of the branch to the brain, blood flow reversal occurs in the branch. Blood from the other vessels of the brain is shunted to the upper limb in a reverse direction. When the affected limb is exercised, the steal becomes more and brain suffers a reduction in blood supply leading to dizziness. This is known as subclavian steal syndrome.