The Collaborative International Dictionary of English v.0.48:

Halfway \Half"way`\, a.
   Equally distant from the extremes; situated at an
   intermediate point; midway; as, at the halfway mark. [WordNet
   sense 1]

   Syn: center(prenominal), middle(prenominal), midway.
        [1913 Webster]

   2. partial. [WordNet sense 2]
      [WordNet 1.5 +PJC]

   3. including only half or a portion; incomplete; as, halfway
      measures. [WordNet sense 3]
      [WordNet 1.5 +PJC]

   Halfway covenant, a practice among the Congregational
      churches of New England, between 1657 and 1662, of
      permitting baptized persons of moral life and orthodox
      faith to enjoy all the privileges of church membership,
      save the partaking of the Lord's Supper. They were also
      allowed to present their children for baptism.
      [1913 Webster]