'blindside' definitions:

Definition of 'blindside'

From: WordNet
verb
Catch unawares, especially with harmful consequences; "The economic downturn blindsided many investors"
verb
Attack or hit on or from the side where the attacked person's view is obstructed

Definition of 'blindside'

From: GCIDE
  • blindside \blindside\, v. t. to attack a person from his blind side; metaphorically, to give a person an unpleasant suprise. He had completed his plan to develop a new office building, but was blindsided by the sudden drop in real estate values. [Webster 1913 Suppl.]