diff --git a/make_helpers/utilities.mk b/make_helpers/utilities.mk
index 45ef12e..efa0ab9 100644
--- a/make_helpers/utilities.mk
+++ b/make_helpers/utilities.mk
@@ -100,3 +100,23 @@
 #
 
 bool-01 = $(if $(call bool,$(1)),1,0)
+
+#
+# Determine whether a variable is defined or not.
+#
+# Parameters:
+#
+#   - $(1): The variable to check.
+#
+# Example usage:
+#
+#     xyz-defined := $(call defined,xyz) # <empty>
+#
+#     xyz :=
+#     xyz-defined := $(call defined,xyz) # <non-empty>
+#
+#     xyz := hello
+#     xyz-defined := $(call defined,xyz) # <non-empty>
+#
+
+defined = $(call bool,$(filter-out undefined,$(origin $(1))))