A backup, safety friend. Usually only contacted when the initial sources of entertainment are MIA.
Omar was nowhere to be found, so we looked for our friendship condom, Chad.
When you don't trust a friend enough to let them get close to you.
When to wear a "friendship condom"? - when you are still friends but you don't open up to them or get close emotionally in fear of them being fake with bad intentions.
She told my boss my secret so now I wear a friendship condom with her.