A humorously-altered/shortened way of saying, "I would imagine so"; it's mostly used to jovially/light-heartedly tell someone else that his guess/assertion about a particular topic --- usually something comparatively minor/trivial --- sounds probable/logical/reasonable to you.
Cool dude #1, examining a discarded trash-bag with medium-length slits in the middle of the bottom and along both its lower sides: I would say that this bag was probably used as an emergency rain-poncho; wouldn't you majjin??
Cool dude #2: Yeah, I majjin --- the bag looks in good shape otherwise, and those slits appear neat and uniformly-positioned, so I don't suppose they got torn accidentally.
Cool dude #2: Yeah, I majjin --- the bag looks in good shape otherwise, and those slits appear neat and uniformly-positioned, so I don't suppose they got torn accidentally.
by QuacksO August 23, 2018