The longer-date option in an option spread. That is, the part of an option spread (such as a calendar spread) which has the far (or later) expiration date. An option spread typically involves buying or selling options with different maturities. Naturally, the far option has more time (and hence bigger chance) to become in the money (in-the-money option) within its time to maturity, and therefore trades for larger premiums.

The far option is the opposite of a near option.