The term 1/1000 of an inch can be abbreviated as MIL, which is a three letter acronym. MIL stands for milliradian, which is a unit of angular measurement equal to one thousandth of a radian. It is also used to measure the thickness of materials such as paper, plastic, and metal. In the context of engineering, MIL is often used to describe the precision of a machined part or the accuracy of a measurement.