Noun
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.
Source: Webster's dictionaryThe new-export-orders subindex, a gauge of external demand, dropped to 28.7 in February from 48.7 in January. Source: Internet
The employment subindex remained in negative territory for the sixth consecutive month, even running weaker than the previous month. Source: Internet