1. the part of one's field of vision, as to the side and rear, where one is unable to see approaching objects.
2. the side opposite that toward which a person is looking.
Pronunciation: (blīnd'sīd"),[key] —v.t.,-sid•ed, -sid•ing. 1. Sports.to tackle, hit, or attack (an opponent) from the blind side: The quarterback was blindsided and had the ball knocked out of his hand. 2. Informal.to attack critically where a person is vulnerable, uninformed, etc.: The president was blindsided by the press on the latest tax bill.