What defensive strategy did General Meade employ at the Battle of Gettysburg

He formed the Union Army into a fishhook formation.

The defensive strategy that General Meade was to place his army in a hook-shaped line, and placed additional soldiers at his flanks. Lee's attack consisted on a massive frontal attack on the center of the line, provoking tremendous losses of men to Lee's confederate army, deriving in a great victory for the Union.