These lines have a practical character. I point out first what one can find on the Internet. Then I discuss a bit the dictionaries in book form that one can find in a library.
Dexonline is a an electronic dictionary. Its name comes from “DEX” (dicţionar explicativ). It has been initiated by Cătălin Frâncu. The project, with the help of volunteers, has created a vast collection of articles about Romanian words from various dictionaries.
The articles from dexonline offer definitions of the meanings of a word. They also illustrate the use of words.
On the Internet, dexonline is available from http://dexonline.ro/. There is also a link on the main page of the web page of the Romanian Ministry of Education. The address at this link is http://dictionare.edu.ro/.
If you want to work offline, you need a special program. There is a list of such programs on the this page. The dixit project uses QT. For more comments see this note.
The most important dictionary of the Romanian language is Dicţionarul limbii române. It is published by Editura Academiei Române.
The Romanian Academy, at 1 January 1906, has taken the decision to publish Dicţionarul limbii române. This is a “dicţionar-tezaur”, which contains, beyond definitions and explanations a vast array of quotations from Romanian authors.
The first editor of Dicţionarul limbii române has been Sextil Puşcariu. The first volume has been published in 1913. This has been the start of the first series of the dictionary and is called DA.
A short history of the Dicţionarul limbii române is included in volume I of the new series of the dictionary (Bucureşti: Editura Academiei, 2006). The new series is called for short DLR.
The students of the Philosophy Department at the University of Bucharest can find some of the volumes from DLR. The shelf number is R80/D39.