diff --git a/documentation/ref-manual/ref-variables.xml b/documentation/ref-manual/ref-variables.xml
index c7904f8e80..90eeb2ec07 100644
--- a/documentation/ref-manual/ref-variables.xml
+++ b/documentation/ref-manual/ref-variables.xml
@@ -16,7 +16,7 @@
 
 
     <para>
-       <link linkend='var-ALLOW_EMPTY'>A</link>
+       <link linkend='var-ABIEXTENSION'>A</link>
        <link linkend='var-B'>B</link>
        <link linkend='var-CFLAGS'>C</link>
        <link linkend='var-D'>D</link>
@@ -46,6 +46,26 @@
 
     <glossdiv id='var-glossary-a'><title>A</title>
 
+        <glossentry id='var-ABIEXTENSION'><glossterm>ABIEXTENSION</glossterm>
+            <glossdef>
+                <para>
+                    Extension to the Application Binary Interface (ABI)
+                    field of the GNU canonical architecture name
+                    (e.g. "eabi").
+                </para>
+
+                <para>
+                   ABI extensions are set in the machine include files.
+                   For example, the
+                   <filename>meta/conf/machine/include/arm/arch-arm.inc</filename>
+                   file sets the following extension:
+                   <literallayout class='monospaced'>
+     ABIEXTENSION = "eabi"
+                   </literallayout>
+                </para>
+            </glossdef>
+        </glossentry>
+
          <glossentry id='var-ALLOW_EMPTY'><glossterm>ALLOW_EMPTY</glossterm>
             <glossdef>
                 <para>