It usually means “encrypted” in iMessage, especially if you saw it near a message or conversation status. iMessage uses end-to-end encryption, so the message is protected while it’s being sent between devices.

What that means

  • Encrypted means the message is scrambled so other people, carriers, or random interceptors can’t read it easily.
  • In iMessage, that’s a normal security feature, not an error.

If you meant something else

  • If you saw just “en” by itself, it could also be slang in some chats, but that’s less likely on iMessage.
  • If you can tell me exactly where it appears, I can narrow it down.

Simple example

If a chat shows that messages are encrypted, it’s basically iPhone saying, “This conversation is private during transit”.

TL;DR: On iMessage, “en” most likely refers to encrypted.