mental reply

When you receive an email and compose a reply in your head but don't actually type and send it.

Deepa: Why didn't you respond to my email?
Eric: I did--you didn't get it?
Deepa: No. When did you send it?
Eric: (checking sent items) Oh, I guess I never did. It must have been a mental reply.

by Jim Kudrik November 08, 2008