diff --git a/book/source/glossary.md b/book/source/glossary.md
index e804683..28eec83 100644
--- a/book/source/glossary.md
+++ b/book/source/glossary.md
@@ -112,6 +112,9 @@ Component
 Component Key
     See {term}`OpenPGP Component Key`.
 
+Compressed Data Packet
+    A {term}`packet` that contains compressed data. It represents a "compressed message". The uncompressed data in turn consists of an {term}`OpenPGP message`, made up of a series of {term}`packets<packet>`.
+
 Compression
     See {term}`Data Compression`.
 
@@ -293,7 +296,7 @@ Life-cycle Management
     See [](self-signatures).
 
 Literal Data Packet
-    A {term}`packet<OpenPGP Signature Packet>` in a {term}`Data Signature` which contains data, that has been signed using a {term}`cryptographic signature`. See [RFC 5.9](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#lit) for more details.
+    A {term}`packet` which contains a payload of data. It represents a "literal message". A literal data packet can for example store data that has been signed using a {term}`cryptographic signature`. See [RFC 5.9](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#lit) for more details.
 
 MAC
     See {term}`Message Authentication Code`.
@@ -333,6 +336,9 @@ OpenPGP Certificate
 OpenPGP Component Key
     An {term}`OpenPGP Primary Key` or {term}`OpenPGP Subkey`. For an in-depth discussion see [](component-keys).
 
+OpenPGP data
+    Any data in OpenPGP format, represented as a series of OpenPGP packets. The data could for example represent an {term}`OpenPGP Certificate`, or an {term}`OpenPGP Signature Packet` combined with plaintext or encrypted data.
+
 OpenPGP Fingerprint
     An OpenPGP Fingerprint is a shorthand representation of an {term}`OpenPGP Component Key`. Fingerprints effectively act as unique identifiers. See [](fingerprint).
      
@@ -345,7 +351,14 @@ OpenPGP Key
     Used either for an {term}`OpenPGP Certificate` (containing public key material and metadata), or for an {term}`OpenPGP Private Key`. See [](/certificates) for an in-depth discussion.
 
 OpenPGP Message
-    A data structure, which contains OpenPGP components such as {term}`OpenPGP Certificate` or {term}`OpenPGP Signature Packet` and plaintext or encrypted data.
+    A series of OpenPGP packets that represents one of the following formats:
+    
+    - an encrypted message
+    - a signed message
+    - a {term}`compressed message<compressed data packet>`
+    - a {term}`literal message<literal data packet>`
+
+    Also see [RFC 10.3](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-openpgp-messages).
 
 OpenPGP Public Key
     See {term}`OpenPGP Certificate`.