The crossword solutions for the term BILLIONTH, IN COMBOS are NANO. The term 'nano' is derived from the Greek word for 'DWARF' and is used as a prefix to denote one-billionth of a unit. It is commonly used in scientific contexts to refer to very small measurements, such as nanometers or nanoseconds. Nano is also used in technology to refer to nanotechnology, which is the manipulation of matter on an atomic, molecular, and supramolecular scale.