A joint made with just one small rolling paper. Generally used if you only have limited weed, you only have small papers available and can't be bothered to make an L-plate or you're smoking by yourself.
Timmie - Hey Harry, can I skin up for you?
Harry - Sorry man, I've only got enough for a single bean.
when everyone you know is in a relationship and your the only one without a person.
Everyone: Omd we've been dating for ages
That 1 person (me) : yea yea ok
Everyone: You're such a single bean , find someone