In biology, this refers to two anatomical structures or behavioral traits within different and unrelated organisms which perform the same functions in each organism but which did not originate from an ancestral structure or trait that the organisms' ancestors had in common. Instead, the structures or traits arose separately and then later evolved to perform the same function (or similar functions). See also convergent evolution. Compare homology.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.