1. When a "friend" asks for deeply discounted pricing on an item you are selling, essentially robbing you of money you could easily make from any average buyer, and you grant it almost exclusively because you'd feel bad if you didn't.
2. When a friend immediately demands payable the privilege of knowing him/her in the form of a discount.
"I'm selling my XBox 360 for $140 on craigslist."
"My XBox just red-ringed. Can I get a friend discount on that?"
A pillow placed between members of the opposite sex (or of compatible sexualities) when sharing a bed for the evening. This pillow is intended to explicitly communicate the desire to abstain from sexual activity of any type, making it "safe" for platonic bed-sharing.
Same as pillow partition, but more used for people who are in relationships and don't want to cheat -- but would totally consider it if they were single.
Male friend: You can have my bed and I'll sleep on the couch.
Female friend: Don't be silly. We'll just put a chastity pillow between us and I'll try to keep my cold feet off you.
Male friend: If you say so.