The Collaborative International Dictionary of English v.0.48:

pipeline \pipeline\, pipe line \pipe line\
   1. A line of pipe with pumping machinery and apparatus for
      conveying liquids, gases, or finely divided solids, such
      as petroleum or natural gas, between distant points.
      [Webster 1913 Suppl. +PJC]

   2. fig. an information channel direct from the source.
      [PJC]

   3. the set of stages and processes from the invention or
      design of a product to its ultimate use, production, or
      commercial sale. Used commonly in the phrase

   in the pipeline, i. e. still in preparation or under
      development.
      [PJC]