i want to make a medium sized glossary which have differnet terms and their description and if the description has a term whose description itself is also available in the db then it should be link to its own description
How to do it ?

A lot of custom programming. You may want to talk with some freelancers.

I would think, look into open sourced projects and maybe customise them a little? ;)

Doesn't the original Wikipedia support this?
I believe you can download it, ...

that's quite a question; I'm not sure what kind of reply your expecting. Are you saying you want a program to be made to do this?

If you know any PHP at all, perhaps customize something, but if you don't, or not very well, then you should probably hire someone.

i can customize code if u can tell me where i can find that

hello ................

Look for a software called "Mediawiki"