noun \??pach\Definition of PATCH1 : a piece of material used to mend or cover a hole or a weak spot 2 : a tiny piece of black silk or court plaster worn on the face or neck especially by women to hide a blemish or to heighten beauty 3 a : a piece of material (as adhesive plaster) used medically usually to cover a wound b : a usually disk-shaped piece of material that is worn on the skin and contai