The Collaborative International Dictionary of English v.0.48:

container ship \container ship\, containership \containership\n.
   a ship designed to hold containerized cargoes.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

containership
    n 1: a cargo ship designed to hold containerized cargoes; "the
         weight of the documentation of all the consignments on
         board a contemporary container ship can exceed 90 pounds"
         [syn: container ship, containership, container
         vessel]