a metric unit of length equal to one billionth of a meter

a billionth of a metre

one billionth of a metre (10-9 metres).

1 × 10-9 m. One millionth of a millimetre, a.k.a. a millimicron; equals ten angstroms.

a millionth of a millimeter, and each chip production technology is measured by the size of the smallest feature it can produce on a chip