1.  octet(n = noun.quantity) 8, eight, eighter, eighter from decatur, octad, octonary, ogdoad, viii - the cardinal number that is the sum of seven and one;
is a kind of digit, figure

2.  octet(n = noun.group) octette - eight performers or singers who perform together;
is a kind of musical group, musical organisation, musical organization

3.  octet(n = noun.group) octette - a set of eight similar things considered as a unit;
is a kind of set

4.  octet(n = noun.group) eightsome, octette - eight people considered as a unit;
is a kind of assemblage, gathering

5.  octet(n = noun.communication) octette - a musical composition written for eight performers;
is a kind of composition, musical composition, opus, piece, piece of music

1.  A composition for eight parts, usually for eight solo instruments or voices. [1913 Webster]

2.  A group of eight singers or eight musicians. [PJC]

octet, n. (also octette)
1 Mus. a a composition for eight voices or instruments. b the performers of such a piece.
2 a group of eight.
3 the first eight lines of a sonnet.
4 Chem. a stable group of eight electrons.

Etymology:
It. ottetto or G Oktett: assim. to OCT-, DUET, QUARTET