Septum \Sep"tum\, n.; pl. Septa. [L. septum, saeptum, an inclosure, hedge, fence, fr. sepire, saepire, to hedge in, inclose.]

1. A wall separating two cavities; a partition; as, the nasal septum.

2. (Bot.) A partition that separates the cells of a fruit.

3. (Zo["o]l.)
   (a) One of the radial calcareous plates of a coral.
   (b) One of the transverse partitions dividing the shell of a mollusk, or of a rhizopod, into several chambers. See Illust. under Nautilus.
   (c) One of the transverse partitions dividing the body cavity of an annelid.

Source: Webster's Revised Unabridged Dictionary (1913)