The Collaborative International Dictionary
Subindices
Subindex \Sub*in"dex\, n.; pl. Subindices. (Math.) A number or mark placed opposite the lower part of a letter or symbol to distinguish the symbol; thus, a0, b1, c2, xn, have 0, 1, 2, and n as subindices.
Wiktionary
subindices
n. (plural of subindex English)
WordNet
subindices
See subindex