1. The plate or plane along which the chromosomes align during metaphase (an intermediate stage of mitosis or meiosis).
  2. An unconnected cytoplasmic membrane which forms in the middle of a cell during early cytokinesis, when the cell is about to divide into two daughter cells.

From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.