Several people have been asking on other genealogy blogs about old medical terms; specifically on death certificates. So I looked for websites that could help.
There are several excellent sites to look up old medical terms. http://www.rootsweb.ancestry.com/~usgwkidz/oldmedterm.htm is an alphabetical list with a simple answer. This website is free.
If you want a more complex explanation of a medical term, you will want to check out http://www.archaicmedicalterms.com that is titled, A Glossary of Archaic Medical Terms, Diseases and Causes of Death. This website is free to lookup but there is a charge to download. You can buy a CD and download for $15 that seemed very reasonable if you would have frequent use of the information.
Checking out the second website with the more in depth explanations, I found that "consumption" (a frequently named cause of death) has the term explained from sources at different time periods. For example, "tuberculous" is not the only answer and is NOT just a substitute term for "consumption" as cause of death. If you had a question about why someone died, you may want to use this source for a greater understanding.
Another thing I really like about this source is the scans of actual old handwriting with the written term. So you can compare the term written on a death certificate to the terms listed. Let me know if this is helpful.