a. and sb. [f. as prec. + -TH.] A. adj. The ordinal adjective corresponding to ‘billion.’ B. sb. The billionth part.
1778. Maseres, Converg. Series, in Phil. Trans., LXVIII. 900. The billionth root of 10 will be = 1.000,000,000,002,302, 585,093.
1865. Draper, Int. Devel. Europe, xxv. 607. The vibrations which thus occasion light are, at a mean, 525 in the billionth of a second.
