The dictionary's definition of a friend:
A person other than a family member, spouse or lover whose company one enjoys and towards whom one feels affection.
Although I agree with the dictionary, My definition of a friend:
Someone who makes you smile when you're down, who you can argue with like a 2 or 5 year old, one you can never stay mad at for too long, but above all you have fun together even if you're just talking.