dissepiment

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Botany A partition dividing an organ, such as an ovary or a fruit, into chambers.

Century Dictionary and Cyclopedia

1. n. In botany: A partition; especially, one of the partitions within ovaries and fruits formed by the coherence of the sides of the constituent carpels. Spurious or false dissepiments are partitions otherwise formed.
2. n. In hymenomycetous fungi, same as trama.
3. n. In zoöl. and anat.: In general, a septum or partition; that which puts asunder two or more things by coming between them: as, the dissepiment of the nostrils.
4. n. Specifically— One of the imperfect horizontal plates which connect the vertical septa in corals, and divide the loculi between the septa into a series of intercommunicating cells. The internal separation or division between the segments of annelids, as worms.

Wiktionary

1. n. botany, zoology partition (in an organ); septum

GNU Webster's 1913

1. n. A separating tissue; a partition; a septum.
2. n. (Bot.) One of the partitions which divide a compound ovary into cells.
3. n. (Zoöl.) One of the transverse, calcareous partitions between the radiating septa of a coral.