Infra/ɪnfrə/ Definition 1 of 3Pro Tip 1/3Physical Location Refers to the actual physical position being below something else. The cables are running infra the floorboards. Pro Tip 2/3Technical Terms Common in technical contexts, especially when discussing layers or levels. You'll find the insulation infra the outer shell of the device. Pro Tip 3/3Not Visible Surface Often used when the lower component is not visible from the surface. Water pipes are installed infra the city streets.