[1] : The Collaborative International Dictionary of English v.0.48

merchant marine \mer"chant marine"\, n.
   the ships owned by nationals of a particular country that are
   engaged in civilian commerce; also, the personnel operating
   those vessels. distinguished from the navy, which contains
   the vessels of war.
   pjc
see also:
navy 

[2] : WordNet (r) 2.0

merchant marine
     n 1: the crew of a merchant vessel
     2: conveyance provided by the ships belonging to one country or
        industry syn: shipping, cargo ships, merchant
        vessels
see also:
shipping cargo ships merchant vessels 

[3] : Moby Thesaurus II by Grady Ward, 1.0

30 moby thesaurus words for "merchant marine":
   naval construction battalion, rn, royal navy, seabees, usn,
   united states navy, argosy, armada, bottoms, coast guard, division,
   escadrille, fleet, flotilla, line, marine, merchant fleet,
   merchant navy, mosquito fleet, naval forces, naval militia,
   naval reserve, navy, shipping, ships, squadron, task force,
   task group, tonnage, whaling fleet

Merchant Marine >> M Words
Merchant Marine, definition of term: Merchant Marine
merchant+marine_pag1.html

Merchant >> M Words
Merchant, definition of term: Merchant
merchant_pag1.html

Marine >> M Words
Marine, definition of term: Marine
marine_pag1.html

Merchant Bank >> M Words
Merchant Bank, definition of term: Merchant Bank
merchant+bank_pag1.html

Merchant Ship >> M Words
Merchant Ship, definition of term: Merchant Ship
merchant+ship_pag1.html

Marine Glue >> M Words
Marine Glue, definition of term: Marine Glue
marine+glue_pag1.html

Marine Acid >> M Words
Marine Acid, definition of term: Marine Acid
marine+acid_pag1.html

Marine Corps >> M Words
Marine Corps, definition of term: Marine Corps
marine+corps_pag1.html

Law Merchant >> L Words
Law Merchant, definition of term: Law Merchant
law+merchant_pag1.html