The Collaborative International Dictionary of English v.0.48:

Dissepiment \Dis*sep"i*ment\, n. [L. dissaepimentum, fr.
   dissaepire; dis- + saepire to hedge in, inclose.]
   1. A separating tissue; a partition; a septum.
      [1913 Webster]

   2. (Bot.) One of the partitions which divide a compound ovary
      into cells.
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   3. (Zool.) One of the transverse, calcareous partitions
      between the radiating septa of a coral.
      [1913 Webster]