Diagonal Spread

An options strategy established by simultaneously entering into a long and short position in two options of the same type (two call options or two put options) but with different strike prices and expiration dates.

Investopedia Says:
This strategy is called a diagonal spread because it combines a horizontal spread, which represents the difference in expiration dates, with a vertical spread, which represents the difference in strike prices. An example of a diagonal spread is the purchase of a December $20 call option and the sale of an April $25 call.

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Strategy based on a long and short position in the same class of option (two puts or two calls in the same stock) at different striking prices and different expiration dates. Example: a six-month call sold with a striking price of 40 and a three-month call sold with a striking price of 35. See also Calendar Spread; Vertical Spread.