an increase in width

Is a term often used in hedging or risk management activities. It refers to an increased spread or price differential between the underlying cash market and the futures market. It can also refer to the differences between two futures contract delivery months or two forward delivery dates.

the act of making something wider

a part of a road that has been widened to allow cars to pass or park

Widening is removing any restriction (q.v.) on the current buffer; it is the opposite of narrowing (q.v.). See section AC.22 Narrowing.