What a casual relationship might end up as for the guy. The male part of the fertilization process. See sperm donor
by Filamena C June 18, 2008

by mk fresh November 8, 2007

your biological father as opposed to your stepfather.
by cheesemac November 1, 2007

The guy that knocked you up and either bailed or you kicked him to the curb. Not involved in the child's life except maybe enforced support payments. If you're a dude, what the baby mama calls you.
Tiffany met her bio-dad for the first time last week. Her first reaction was "What was Mom thinking?"
by sendmorecoffee August 1, 2008

by Safffernellie December 5, 2009
