un·de·cil·lion 
(un′dĭ-sĭlyən)
(un′dĭ-sĭlyən)n.
1. The cardinal number equal to 1036.
2. Chiefly British The cardinal number equal to 1066.
[Latin undecim, ūndecim (ūnus, one; see oi-no- in the Appendix of Indo-European roots + decem, ten; see dek in the Appendix of Indo-European roots) + (M)ILLION.]
un′de·cillion adj.
un′de·cillionth adj., adv. & n.