Definition from Wiktionary, the free dictionary
Old English seldan.
- infrequently, rarely.
- They seldom come here now.
- 2013 April 9, Andrei Lankov, “Stay Cool. Call North Korea’s Bluff.”, New York Times:
- People who talk about an imminent possibility of war seldom pose this question: What would North Korea’s leadership get from unleashing a war that they are likely to lose in weeks, if not days?
Usage notes 
- Compare He seldom ever plays tennis. with He almost never plays tennis.