Short definition
American Viticultural Area — a legally defined grape-growing region in the United States based on geographic and climate characteristics.
Unlike European appellations, an AVA only guarantees geography — it says nothing about which grapes were used or how the wine was made. Napa Valley, Willamette Valley, and Sonoma Coast are all AVAs. If a wine lists an AVA, at least 85% of the grapes must come from that area. AVAs can nest inside each other: Rutherford is an AVA within Napa Valley, which is an AVA within North Coast.