de·fo·cus 
(dē-fōkəs)
(dē-fōkəs)tr.v. de·fo·cused, de·fo·cus·ing, de·fo·cus·es or de·fo·cussed or de·fo·cus·sing or de·fo·cus·ses
To cause (a beam or a lens) to deviate from accurate focus.
n.
The act or result of causing a lens to deviate from accurate focus.