http://www.fao.org/biotech/index_glossary.asp. Glossary of biotechnology and genetic engineering by Food and Agriculture Organization of the United Nations. This site provides a tabbed list of words and their definitions, but no search function. Online searches are free. There is a bound book version of the dictionary available for sale.
http://filebox.vt.edu/cals/cses/chagedor/glossary.html. . Agricultural and Environmental Biotechnology Dictionary by Susan Allender-Hagedorn and Charles Hagedorn, Virginia Tech Univ. This site provides a list of terms and definitions, but no tabs or search functions.
http://biotechterms.org/sourcebook/index.phtml . . Glossary of Biotechnology Terms by Monsanto & Technomic Publishing Company. This site will search for a word, or allow scanning lists of words organized by first letter. Online searches are free. There is a bound book version of the dictionary available for sale.