Not as good as a real friend but you use one from time to time to fill a need.
Not someone you would ahng out with long term, a temporary solution to boredom/loneliness.
Someone you pick up when you need them and go without when you dont.
Can be applied to same-sex and opposite sex relationships, of the platonic or sexual nature.
In most cases the nature of the McFriendship goes one way, with one person being the consumer and the other the provider.
the person you email when bored at work because you know they will reply
the person you hook up with at the end of a night in town because they are there and you didnt pick up anyone else
cara: hey beth do you wana go out tonight?
cara: can you drive? i have no money
beth: you are such a user am i just a mcfriend to you??
adam: did you hook up with beth again last night? do you like her or something?
jimmy: nah shes just my mcfriend