Shear or Shearing:  a strain in the structure of a substance or assembly produced by opposing forces, when its layers are laterally shifted in relation to each other.  This is often used to define movement between two construction components which move opposite one another in different directions such as two sheets of drywall at the corners of a room.  In construction shearing between components can occur due to movement caused by deflection of a foundation, structure, or can be caused by other forces.