A thick and heavy patterend cardigan, as rocked by stoners and associated social groups. The tripper rug offers the perma-baked warmth and comfort as well as some psychological security whilst venturing into the world to forage for supplies, or heaven forbid, to occasionally do something productive.
A classic example of the tripper rug and its wearer would be the dude (Jeff Bridges) in The Big Lebowski.
Saw my old stoner
Uni buddy for the first time for ages yesterday, he's still the same, still stoned
in the day time wandering round town with his tripper rug