peripheralpe·riph·e·ral /pəˈrɪfərəl/ adjectiveadj1peripheral activity/ business etcCOMMERCE an activity, business etc that is not the most important one that a company is involved inThe firm is neglecting profitable core businesses to develop peripheral activities.
2peripheral equipment/productCOMPUTING equipment that is connected to a computer and used with itThe company focused on supplying peripheral products such as printers.
—peripheral noun [countableC]a maker of computer peripherals, particularly disk drives