In standard dropdowns, you can hit Escape (on your keyboard) to cancel form entry and close the dropdown.

Gh-16

chosen/chosen.jquery.js

@@ -607,8 +607,12 @@
             return this.result_select();
           }
           break;
+        case 27:
+          if (this.results_showing) {
+            return this.results_hide();
+          }
+          break;
         case 9:
-        case 13:
         case 38:
         case 40:
         case 16:

chosen/chosen.proto.js

@@ -610,8 +610,12 @@
             return this.result_select();
           }
           break;
+        case 27:
+          if (this.results_showing) {
+            return this.results_hide();
+          }
+          break;
         case 9:
-        case 13:
         case 38:
         case 40:
         case 16:

coffee/chosen.jquery.coffee

@@ -520,7 +520,9 @@ class Chosen
       when 13
         evt.preventDefault()
         this.result_select() if this.results_showing
-      when 9, 13, 38, 40, 16
+      when 27
+        this.results_hide() if @results_showing
+      when 9, 38, 40, 16
         # don't do anything on these keys
       else this.results_search()
 

coffee/chosen.proto.coffee

@@ -513,7 +513,9 @@ class Chosen
       when 13
         evt.preventDefault()
         this.result_select() if this.results_showing
-      when 9, 13, 38, 40, 16
+      when 27
+        this.results_hide() if @results_showing
+      when 9, 38, 40, 16
         # don't do anything on these keys
       else this.results_search()