means A market in which a single buyer dominates, giving that buyer the power to dictate terms to many competing sellers (such as a lone employer in a one-company town).

from Coined by economists in the early 20th century from Greek roots: monos, 'single,' plus opsōnia, 'buying of provisions' (the kind of word that once meant haggling for fish and meat at market). It was deliberately built as the mirror-image of 'monopoly,' which pairs monos with pōlein, 'to sell' — so monopoly is one seller, monopsony one buyer. The coinage is often credited to the Cambridge economist Joan Robinson, who popularized the term in the 1930s.