de·fo·cus  (dē-fō'kəs)  tr.v. de·fo·cused or de·fo·cussed, de·fo·cus·ing or de·fo·cus·sing, de·fo·cus·es 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. |