diff --git a/src/cowboy_swagger.erl b/src/cowboy_swagger.erl
index 4cccdb2..5342016 100644
--- a/src/cowboy_swagger.erl
+++ b/src/cowboy_swagger.erl
@@ -2,7 +2,7 @@
 -module(cowboy_swagger).
 
 %% API
--export([to_json/1]).
+-export([to_json/1, add_definition/2]).
 
 %% Utilities
 -export([enc_json/1, dec_json/1]).
@@ -19,6 +19,7 @@
    , description => iodata()
    , required    => boolean()
    , type        => iodata()
+   , schema      => iodata()
    }.
 -export_type([parameter_obj/0]).
 
@@ -28,6 +29,20 @@
 -type responses_definitions() :: #{binary() => response_obj()}.
 -export_type([response_obj/0, responses_definitions/0]).
 
+-type parameter_definition_name () :: binary().
+-type property_obj() ::
+  #{binary() =>
+      #{ type => binary()
+       , description => binary()
+       , example => binary()
+       }}.
+-type parameters_definitions() ::
+  #{parameter_definition_name() =>
+      #{ type => binary()
+       , properties => property_obj()
+       }}.
+-export_type([parameter_definition_name/0, property_obj/0]).
+
 %% Swagger map spec
 -opaque swagger_map() ::
   #{ description => iodata()
@@ -60,6 +75,19 @@ to_json(Trails) ->
                             basePath => ApiRoot},
   enc_json(SwaggerSpec).
 
+-spec add_definition( Name::parameter_definition_name()
+                    , Properties::property_obj()
+                    ) ->
+  ok.
+add_definition(Name, Properties) ->
+  Definition = build_definition(Name, Properties),
+  SwaggerSpec = application:get_env(cowboy_swagger, global_spec, #{}),
+  ExistingDefinitions = maps:get(definitions, SwaggerSpec, #{}),
+  NewDefinitions = #{definitions => maps:merge( ExistingDefinitions
+                                              , Definition
+                                              )},
+  application:set_env(cowboy_swagger, global_spec, NewDefinitions).
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %% Utilities.
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@@ -175,3 +203,13 @@ validate_swagger_map_params(Params) ->
 validate_swagger_map_responses(Responses) ->
   F = fun(_K, V) -> V#{description => maps:get(description, V, <<"">>)} end,
   maps:map(F, Responses).
+
+%% @private
+-spec build_definition( Name::parameter_definition_name()
+                      , Properties::property_obj()
+                      ) ->
+  parameters_definitions().
+build_definition(Name, Properties) ->
+  #{Name => #{ type => <<"object">>
+             , properties => Properties
+             }}.
diff --git a/test/cowboy_swagger_SUITE.erl b/test/cowboy_swagger_SUITE.erl
index 6171a1f..701e85c 100644
--- a/test/cowboy_swagger_SUITE.erl
+++ b/test/cowboy_swagger_SUITE.erl
@@ -9,7 +9,7 @@
        ]).
 
 -export([all/0]).
--export([to_json_test/1]).
+-export([to_json_test/1, add_definition_test/1]).
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %% Common test
@@ -120,6 +120,48 @@ to_json_test(_Config) ->
   3 = maps:size(Paths),
   {comment, ""}.
 
+-spec add_definition_test(Config::cowboy_swagger_test_utils:config()) ->
+  {comment, string()}.
+add_definition_test(_Config) ->
+  ct:comment("Add first definition"),
+  Name1 = <<"CostumerDefinition">>,
+  Properties1 =
+    #{ <<"first_name">> =>
+        #{ type => <<"string">>
+         , description => <<"User first name">>
+         , example => <<"Pepito">>
+         }
+    , <<"last_name">> =>
+        #{ type => <<"string">>
+         , description => <<"User last name">>
+         , example => <<"Perez">>
+         }
+    },
+  ok = cowboy_swagger:add_definition(Name1, Properties1),
+  {ok, SwaggerSpec} = application:get_env(cowboy_swagger, global_spec),
+  Definition1 = maps:get(definitions, SwaggerSpec),
+
+  ct:comment("Add second definition"),
+  Name2 = <<"CarDefinition">>,
+  Properties2 =
+    #{ <<"brand">> =>
+        #{ type => <<"string">>
+         , description => <<"Car brand">>
+         }
+    , <<"year">> =>
+        #{ type => <<"string">>
+         , description => <<"Production time">>
+         , example => <<"1995">>
+         }
+    },
+  ok = cowboy_swagger:add_definition(Name2, Properties2),
+  {ok, SwaggerSpec1} = application:get_env(cowboy_swagger, global_spec),
+  JsonDefinitions = maps:get(definitions, SwaggerSpec1),
+  true = maps:is_key(Name1, JsonDefinitions),
+  true = maps:is_key(Name2, JsonDefinitions),
+
+  {comment, ""}.
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %% Internal functions
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%