diff --git a/glossary.md b/glossary.md
index 1b7b57c20d..12c0ca177e 100644
--- a/glossary.md
+++ b/glossary.md
@@ -18,3 +18,5 @@ You may also need to check <https://chromium.googlesource.com/chromiumos/docs/+/
   primarily administrated by Matt Godbolt.
 * primordials: Pristine built-ins that are not affected by prototype pollution
   and tampering with built-ins.
+* undici: An alternative HTTP client used in Node.js. See more details
+  on the [undici repository](https://github.com/nodejs/undici).