diff --git a/main.c b/main.c
index 8ca82fc..405c9a3 100644
--- a/main.c
+++ b/main.c
@@ -452,6 +452,7 @@ usage(void)
 
 	printf("\nquerying specific pkg-config database fields:\n\n");
 
+	printf("  --define-variable=varname=value   define variable 'varname' as 'value'\n");
 	printf("  --variable=varname                print specified variable entry to stdout\n");
 	printf("  --cflags                          print required CFLAGS to stdout\n");
 	printf("  --cflags-only-I                   print required include-dir CFLAGS to stdout\n");
@@ -506,6 +507,7 @@ main(int argc, char *argv[])
 		{ "no-uninstalled", no_argument, &want_no_uninstalled, 25, },
 		{ "keep-system-cflags", no_argument, &want_keep_system_cflags, 26, },
 		{ "keep-system-libs", no_argument, &want_keep_system_libs, 26, },
+		{ "define-variable", required_argument, NULL, 27, },
 		{ NULL, 0, NULL, 0 }
 	};
 
@@ -525,6 +527,9 @@ main(int argc, char *argv[])
 		case 11:
 			maximum_traverse_depth = atoi(optarg);
 			break;
+		case 27:
+			pkg_tuple_define_global(optarg);
+			break;
 		default:
 			break;
 		}
diff --git a/pkg.h b/pkg.h
index 426929f..acafe89 100644
--- a/pkg.h
+++ b/pkg.h
@@ -169,5 +169,6 @@ void pkg_tuple_free(pkg_tuple_t *head);
 void pkg_tuple_add_global(const char *key, const char *value);
 char *pkg_tuple_find_global(const char *key);
 void pkg_tuple_free_global(void);
+void pkg_tuple_define_global(const char *kv);
 
 #endif
diff --git a/tuple.c b/tuple.c
index 820fd89..12c7a52 100644
--- a/tuple.c
+++ b/tuple.c
@@ -52,6 +52,22 @@ pkg_tuple_free_global(void)
 	pkg_tuple_free(pkg_global_var);
 }
 
+void
+pkg_tuple_define_global(const char *kv)
+{
+	char *workbuf = strdup(kv);
+	char *value;
+
+	value = strchr(workbuf, '=');
+	if (value == NULL)
+		goto out;
+
+	*value++ = '\0';
+	pkg_tuple_add_global(workbuf, value);
+out:
+	free(workbuf);
+}
+
 pkg_tuple_t *
 pkg_tuple_add(pkg_tuple_t *parent, const char *key, const char *value)
 {