David and Goldberg (1957)
Agribusiness is the sum total of all operations involved in thr manufacture and distribution of farm supplies;  production activities on the farm; and storage, processing and distribution of farm commodities and items made from them.

Beierlein and Woolverton (1991)
Agribusiness includes not only those that farm the land but also the people and firms that provide inputs (e.g, milk, grain, meat), manufacture the food products (e.g., ice cream, bread, breakfast cereals), and transport and sell the food products to consumers (e.g., restaurants, supermarkets).

The food and fiber syatem is increasingly being refered to as agribusiness.

Schaffner, Schoder and Earle (1998)
The food syatem includes supplies of farm inputs, agricultural producers, suppliers of fish and game, producers of fermentation products, packaging suppliers, processors and manufacturers, commodity merchants, wholesalers, food retailers, restaurants, institutions, and facilitating industries, such as transport, finance and future markets.