The Collaborative International Dictionary of English v.0.48:

bioassay \bioassay\ n.
   appraisal of the biological activity of a substance by
   testing its effect on an organism.
   [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

bioassay \bioassay\ v. 1
   to subject to a bio-assay.

   Syn: bio-assay.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

bio-assay
    n 1: appraisal of the biological activity of a substance by
         testing its effect on an organism and comparing the result
         with some agreed standard [syn: bioassay, bio-assay]