What is Backspread?

Legal Definition
The backspread is the converse strategy to the ratio spread and is also known as reverse ratio spread. Using calls, a bullish strategy known as the call backspread can be constructed and with puts, a strategy known as the put backspread can be constructed.
-- Wikipedia
Legal Definition
An OPTION strategy designed to take advantage of VOLATILITY. A LONG back spread is created through the sale of a smaller quantity of closertothemoney PUT OPTIONS or CALL OPTIONS and the purchase of a larger quantity of fartherfromthemoney puts or calls. See also RATIO VERTICAL SPREAD.