The nanometer is a unit of measure – just like inches, feet, and miles. A nanometer is a one-billionth of a meter, and used to measure things that are very, very small. Shaquille O’Neal, a very tall basketball player, is 2,160,000,000 nanometers tall! A nanometer is a unit of measure. Just like inches, feet and miles. By definition a nanometer is one-billionth of a meter.