diff --git a/documentation/ref-manual/ref-variables.xml b/documentation/ref-manual/ref-variables.xml
index 160b068c97..a2a5241885 100644
--- a/documentation/ref-manual/ref-variables.xml
+++ b/documentation/ref-manual/ref-variables.xml
@@ -9063,6 +9063,27 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
             </glossdef>
         </glossentry>
 
+        <glossentry id='var-TUNEABI'><glossterm>TUNEABI</glossterm>
+            <glossdef>
+                <para>
+                    An underlying Application Binary Interface (ABI) used by
+                    a particular tuning in a given toolchain layer.
+                    Providers that use prebuilt libraries can use
+                    <filename>TUNEABI</filename> to check compatibility
+                    of a tuning against their selection of libraries.
+                </para>
+
+                <para>
+                    The OpenEmbedded build system checks this variable for
+                    "True" or "".
+                    If the variable is undefined, then every tune is allowed.
+                    See the
+                    <link linkend='ref-classes-sanity'><filename>sanity</filename></link>
+                    class to see how the variable is used.
+                </para>
+            </glossdef>
+        </glossentry>
+
         <glossentry id='var-TUNECONFLICT'><glossterm>TUNECONFLICT[&lt;feature&gt;]</glossterm>
             <glossdef>
                 <para>