There are many dictionaries of art terms and companions on art and art history in the reference room in Marquand, just to the left upon entering the library. See the section beginning with N33.
Search the Grove Dictionary of Art (online: Oxford Art Online), or do a subject search in the catalog. The latter takes practice, but can be very powerful – be as specific as possible. Library of Congress Subject Headings (used in the catalog), involve a string of terms and are “left-anchored,” so you can browse a particular topic by doing a search, and then examining all its subheadings, e.g. Photography or Archaeology (numerous sub-headings, by time period, by region, by theme). Subject Headings can be people, media (painting, sculpture), themes (Cubism), countries, specific artists (last name, first name), etc. Use the guides in the catalog to help you. For example, if you search for Archaeology as a Subject, click on the "Note" icon for more information about this subject, along with related terms. If you try “Chinese Bronzes” as a subject, you will get no results, but a "More Info" box will appear. Click on this, and it will tell you to use “Bronzes, Chinese” instead.
Oxford Bibliographies is a tremendous resource for annotated bibliographies covering current scholarship that fall within a number of Subject Areas, Art History, being one of them. See the list of all topics covered under Art History here towards the bottom, along with forthcoming topics.
Also, good overviews on various art historical movements, types of art, and specific artists can be found in the World of Art series. In the library catalog, select Advanced Search at the top, do a Series Title search with World of Art. One can do the same thing with other general art historical series. Examples: Pelican History of Art, Oxford History of Art, Dictionaries of Civilization, Sources and Documents in the History of Art, Wiley-Blackwell Companions to Art History, A Guide to Imagery (J. Paul Getty Museum), Art & Ideas (Phaidon), Documents of Contemporary Art (Whitechapel Gallery/MIT Press), Wiley's Art History Special Issue Book Series, A Closer Look (National Gallery, London), How to Read (Metropolitan Museum), and Looking at ________: A Guide to Technical Terms (J. Paul Getty Museum).