meaning - large forehead
Originated at Parklands Secondary school, Bexley, (UK) in 1970's
On his first day at the school, follically challenged and slightly effiminate French Language Teacher Mr Samuel Pam was powerless to prevent 1,200 boys adopting a new craze of slapping each others foreheads and coining the phrase Spamhead after we saw that he signed his name SPAM on our report cards.
Mr Pam valliantly endured 12 years of this torture before taking early retirement.
Term later went on to be used as a general discription for anyone who committed the cardinal sin of being boffin or acting a "bit gay"
Teacher - "why did you hit Jones?"
Boy A - "Well, he was being a spamhead"
Boy B - "No i'm not he spammed me for nuffink!