diff --git a/doc/efun/expand_define b/doc/efun/expand_define
new file mode 100644
index 0000000..c6ff189
--- /dev/null
+++ b/doc/efun/expand_define
@@ -0,0 +1,24 @@
+SYNOPSIS
+        string expand_define (string name)
+        string expand_define (string name, string arg, ...)
+
+DESCRIPTION
+        Expands the macro <name> with the argument(s) <arg>... (default is
+        one empty string "").
+        Result is the expanded macro, or 0 if there is no macro with
+        that name.
+
+        This efun is applicable only while an object is compiled,
+        therefore its usage is restricted to a few functions like the
+        H_INCLUDE_DIRS driver hook, or the masters runtime_error()
+        function.
+
+EXAMPLE
+        While compiling 'foo.c':
+          expand_define("__FILE__") --> "foo.c"
+
+HISTORY
+        Introduced in 3.2.1@93.
+
+SEE ALSO
+        hooks(C), runtime_error(M)