Ctrl+Q currently does not close gnome-dictionary. This is inconsistent with expected keyboard binding behaviour in comparison to most, if not all other gnome desktop applications. Please accept and merge this (diff -u) patch in to gnome-dictionary:

--- gdict-app-menus.ui	2016-03-22 03:15:31.000000000 -0500
+++ gdict-app-menus.ui.ctrlq	2017-01-23 21:11:14.385757543 -0600
@@ -24,8 +24,9 @@
         <attribute name="action">app.about</attribute>
       </item>
       <item>
-        <attribute name="label" translatable="yes">Quit</attribute>
+        <attribute name="label" translatable="yes">_Quit</attribute>
         <attribute name="action">app.quit</attribute>
+	<attribute name="accel">&lt;Primary&gt;Q</attribute>
       </item>
     </section>
   </menu>

so as to better conform with the rest of the standard gnome desktop applications conventions (e.g. gedit, etc.). Perhaps a version bump --> 3.20.1 would be appropriate(?), though this may be unwarranted. Running on Fedora 25 Gnome v3.22.2, in case anyone is wondering.