The Collaborative International Dictionary of English v.0.48:

Diaster \Di*as"ter\, n. [Gr. di- = di`s- twice + ? star.]
   (Biol.)
   A double star; -- applied to the nucleus of a cell, when,
   during cell division, the loops of the nuclear network
   separate into two groups, preparatory to the formation of two
   daughter nuclei. See Karyokinesis.
   [1913 Webster]