This word can be commonly found in some of the episodes of the popular web series, Red vs. Blue (Season 4). It is the name of a foul object that apparently has no equivalent on Earth. The closest to an equivalent on Earth is the defecation produced from the defecation of a skunk.
Gary: What is the foulest smelling animal on your planet?
Tucker: What? Like a skunk?
Gary: Does this skunk defecate?
Tucker: Well, yeah.
Gary: Does that defecation defecate?
Tucker: No, that’s gross!
Gary: Then no; there is no equivalent to a shiznu on your planet, shiznu.
Tucker: What? Like a skunk?
Gary: Does this skunk defecate?
Tucker: Well, yeah.
Gary: Does that defecation defecate?
Tucker: No, that’s gross!
Gary: Then no; there is no equivalent to a shiznu on your planet, shiznu.
by Boris Papovich February 12, 2007