Crammed. Full. And yet, somehow, not overflowing. Something that is jampacked is something of incredible density, where the force in question had to work quite long and hard to get all the various stuff into the container. Cars are frequently jampacked, with people or with luggage. It has been suggested that for particular models of cars, particularly the Geo Metro and the Volkswagon bug, there is no limit to the amount of stuff that may be jampacked into them.