Are you looking for one easy word to describe spam or a description of spam in plain English?
If you're looking for a definition of spam in plain English, I'd go with the unwanted, and often prolific, solicitation of goods, services, or for money or backlinks via e-mail, blogs, search engines, or forums.
The one word I'd use to describe spam would be virulent.
Attention: "role based name" email prefixes such as support, webmaster, info, contact, forum, service, affiliate, admin, traffic, partners, marketing, etc., for our member accounts are not permitted. They are acceptable for a vendor listing, but not for the member email. This is due to bulk email processors scrubbing them for delivery due to extremely high bounce rates. Please apply for membership using a personalized email prefix. Something like firstname.lastname@example.org.
If we discover you signed up with a role based name we will give you only one message to change it. After 3 days your account will be removed if the email is not changed.