Wiktionary
sextillionth
a. The ordinal form of the number sextillion. n. 1 The person or thing in the sextillionth position. 2 One of a sextillion equal parts of a whole.
Usage examples of "sextillionth".
Of this substance, carried to the sextillionth degree, so much as one or two globules of the size mentioned can convey is a common dose.