What is the meaning of sub-paragraph 3-9-6 j. in FAA JO 7110.65X?
If you search for the words "opposite direction" in the order it seems clear that they simply mean what they say, e.g. 3-9-7(a)(1):


  Separate a small aircraft weighing 12,500 lbs. or less taking off from
  an intersection on the same runway (same or opposite direction
  takeoff) [...]


This is confirmed in JO7210.3AA, Facility Operation and Administration:


  2−1−31. OPPOSITE DIRECTION OPERATIONS  
  
  Opposite Direction Operations consists of IFR/VFR Operations conducted
  to the same or parallel runway where an aircraft is operating in a
  reciprocal direction of another aircraft arriving, departing, or
  conducting an approach.