There are really 3 different concepts here.
There is MTA level forwarding (e.g. Unix .forward file) which simply
rewrites the SMTP envelope recipient. Note that MTA level functions
shouldn't alter the headers (other than adding Received). This can
generate an RFC 1891 notification. The term "forwarding address" is
well-known and tightly bound to this concept.
There is MUA level forwarding (e.g. "forward" command in most MUAs) which
encapsulates the message with explainatory information.
There is Resending (also "bounce" or "redirect") which is an MUA level
action which adds Resent headers but doesn't alter the message body.
If necessary, we can just define these three concepts in each document to
keep things clear.