Someone you only call when your real friends are busy.
I was really bored, so I hung out with my side friend.
by mike937 May 04, 2016
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A side friend is a person you are 'friends' with because your other friend is friends with them. So basically your just friends with them because your friend Becky is too. So when you, Becky and that person are all talking, you guys are all considered friends, but if you were left alone with that side friend, it would be awkward to keep a convo going because you guys aren't really friends without Becky there.

You consider your side friend as one of your friends, but deep down inside you know you guys don't really talk without someone thats both of your friends.
"Me and Emma are side friends, if we were left alone it would be so weird"
by Crackers and Cheese April 24, 2017
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A person in which you have developed a friendship with but you are also having sexual relations with this person as well.
That’s be my side- friend through out my whole relationship
by Side friend December 10, 2017
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