Foil/fɔɪl/ Definition 1 of 4Pro Tip 1/3Kitchen Essential Often used in cooking contexts to describe material for wrapping or covering food. Place the chicken on a sheet of foil before baking. Pro Tip 2/3Heat Conductor Foil is mentioned in contexts where heat reflection or preservation is needed. Wrap potatoes in foil to grill them evenly. Pro Tip 3/3Preservation Foil is often referred to as a means of preserving food's freshness. Cover the leftovers with foil to keep them fresh.