salaam ,
jazak Allah ..actually what i meant was a sort of glossary where u find a word mentioned in many places in the quran .. how do u find that out .
The best such reference is the Egyptian book, "The indexed dictionary of the words of the noble Quran" by the late Muhammad Fuaad Abdul-Baaqi, may God reward him handsomely. He spent 17 years compiling it by hand as he lived and died before the computer age.
I don't know if it's available online.
It doesn't have definitions. For that you may find another book helpful: "The unfamiliar words of the Quran" (Ghareeb Al-Quran) by Al-Suyooti and I'm sure there are many other, in addition to Arabic dictionaries, such as Al-Mu`jam Al-Waseet.