— quadrillionth , n. , adj.
/kwo dril"yeuhn/ , n. , pl. quadrillions , ( as after a numeral ) quadrillion , adj.
n.
1. a cardinal number represented in the U.S. by 1 followed by 15 zeros, and in Great Britain by 1 followed by 24 zeros.
adj.
2. amounting to one quadrillion in number.
[ 1665-75; QUADR- + -illion (as in million ) ]