WordWeb Online

1. At half the distance; at the middle
   "he was halfway down the ladder when he fell";
   - midway

1. Equally distant from the extremes
   - center [US], middle, midway, centre [Brit, Cdn]
    
2. At a point midway between two extremes
   "at the halfway mark"
    
3. Including only half or a portion
   "halfway measures"

See also: central, fractional, intermediate, partial

Encyclopedia: Halfway, Or