-Adjective used to describe when someone falls asleep in an upright position, most commonly in a public or semi-public environment. You are able to observe the "scrump" (folds/rolls of excess skin) of the neck as their head falls forward or to one side.
In many circles of friends the act of scrumpy neckin' is an open invitation for public humiliation and shameful photo opportunity. Especially when one is caught scrumpy neckin' with shoes on.
Yeah, I saw him in that comfy chair in the living room scrumpy neckin' like a fool... he must be exausted!