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

open door \o"pen door\
      a open or free admission to all; hospitable welcome;
          free opportunity.
          webster 1913 suppl.

                she of the open soul and open door,
                with room about her hearth for all mankind.
                                                  --lowell.
          webster 1913 suppl.
      b in modern diplomacy, opportunity for political and
          commercial intercourse open to all upon equal terms,
          esp. with reference to a nation whose policy is wholly
          or partially fixed by nations foreign to itself, or to
          territory newly acquired by a conquering nation. in
          this sense, often used adjectively, as, open-door
          system, open-door policy, etc.
          webster 1913 suppl.

                the steps taken by britain to maintain the open
                door have so far proved to be perfectly futile.
                                                  --a. r.
                                                  colquhoun.
          webster 1913 suppl.

[2] : WordNet (r) 2.0

open door
     n 1: the policy of granting equal trade opportunities to all
          countries syn: open-door policy
     2: freedom of access; "he maintained an open door for all
        employees"
see also:
open-door policy 

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

65 moby thesaurus words for "open door":
   eisenhower doctrine, monroe doctrine, nixon doctrine,
   truman doctrine, access, amiability, appeasement, balance of power,
   bonhomie, brinkmanship, coexistence, colonialism, compromise,
   containment, cordiality, detente, deterrence, diplomacy,
   diplomatic, diplomatics, dollar diplomacy, dollar imperialism,
   entrance, entree, entry, expansionism, foreign affairs,
   foreign policy, friendliness, generosity, geniality,
   good-neighbor policy, graciousness, heartiness, hospitableness,
   hospitality, imperialism, in, internationalism, isolationism,
   liberality, manifest destiny, militarism, nationalism,
   neighborliness, neocolonialism, neutralism, nonresistance,
   open arms, open-door policy, openheartedness, opening,
   peace offensive, peaceful coexistence, preparedness, receptiveness,
   shirt-sleeve diplomacy, shuttle diplomacy, spheres of influence,
   the big stick, tough policy, warmheartedness, warmness, warmth,
   world politics

Door >> D Words
Door, definition of term: Door
door_pag1.html

Fly Open >> F Words
Fly Open, definition of term: Fly Open
fly+open_pag1.html

Fire Door >> F Words
Fire Door, definition of term: Fire Door
fire+door_pag1.html

Dutch Door >> D Words
Dutch Door, definition of term: Dutch Door
dutch+door_pag1.html

Back Door >> B Words
Back Door, definition of term: Back Door
back+door_pag1.html