The man that your poor mother mated with to produce you...usually used instead of the term "biological father", where you now have a "new dad" or you don't want to refer to him as your "real" dad.
Daughter: My sperm dad is so cheap he sent me a roll of masking tape for my 12th birthday.
Friend: Well he is from Christchurch (New Zealand)
Friend: Well he is from Christchurch (New Zealand)
by Miss Polly January 25, 2008