A quantity of weed (enough for two people or more) brought along when visiting an important person or good friend, where there is a good possibility of blazing
up in the first place. Considered good manners, so as to not impose on the hosts own supply too much, if at all.
"If we're going to be hanging with Arlo Guthrie, we had better bring some courtesy dope along. It's the least we can do."