InteliHealth online medical dictionary

http://www.intelihealth.com/IH/ihtIH/WSIH=/9276/9276.html

Free online version of the Merriam Webster Medical Dictionary

MEDLINEplus: Medical Dictionary

http://www.nlm.nih.gov/medlineplus/mplusdictionary.html

MedlinePlus free online medical dictionary

Medical Terms from WebMD

http://www.medterms.com/script/main/hp.asp

MedTerms medical dictionary is the medical reference for MedicineNet.com whose doctors define over 16,000 difficult medical terms in easy-to-understand explanations.