the side opposite to the direction in which a person is looking
See blind side in American Heritage Dictionary 4
noun
The side on which one's vision, especially the peripheral vision, is limited or obstructed.
The side away from which one is directing one's attention.
or blind·side(blīndˈsīdˌ)
transitive verbblind-sid·ed or blind·sid·ed, blind-sid·ing or blind·sid·ing, blind-sides or blind·sides
To hit or attack on or from the blind side.
To catch or take unawares, especially with harmful or detrimental results: “The recent recession, with its wave of corporate cost-cutting, blind-sided many lawyers”(Aric Press).