I see your point in so far as that it's fine to come up with and use one's own definitions for words, although every widely accepted definition of e-mail "spam" includes a criterion of being unsolicited. For example, in:
* law (e.g. CAN-SPAM or the Privacy and Electronic Communications Regulations 2003) - indeed CAN-SPAM even stands for Controlling the Assault of Non-Solicited Pornography And Marketing Act and reflects the US government's position, the EU's regulations refer to 'unsolicited communications' - http://www.legislation.gov.uk/uksi/2003/2426/regulation/22/m...
* law (e.g. CAN-SPAM or the Privacy and Electronic Communications Regulations 2003) - indeed CAN-SPAM even stands for Controlling the Assault of Non-Solicited Pornography And Marketing Act and reflects the US government's position, the EU's regulations refer to 'unsolicited communications' - http://www.legislation.gov.uk/uksi/2003/2426/regulation/22/m...
* encyclopedia (say, Wikipedia - http://en.wikipedia.org/wiki/Spamming - or the Encyclopedia Britannica - http://www.britannica.com/EBchecked/topic/941678/spam)
* dictionaries (say, Websters - http://www.merriam-webster.com/dictionary/spam - or the Oxford - http://www.oxforddictionaries.com/definition/english/spam)
* technical standards (say, RFC2505 - http://tools.ietf.org/html/rfc2505)
* the viewpoint of people extremely against spam, such as Spamhaus - http://www.spamhaus.org/consumer/definition/ or SpamCop - http://www.spamcop.net/fom-serve/cache/14.html
* the terms and conditions of e-mail service providers and senders - e.g. http://mailchimp.com/legal/terms/