spread-betting noun a form of gambling against a bookmaker’s predicted result (see citation) US
The “spread” in spread-betting is a pair of values, usually a point or two apart, which represent the bookmaker’s favoured outcome. The investor has two choices: to bet higher, known as “buying”, or bet lower, known as “selling” . — David Bennet, KnowYourBets, p. 107, 2001