Crazy, insane, mentally ill, perturbing, twisted.
Not a good thing.
Usually descriptive of a general mental state, including one of complete obliviousness, but can be used to reference violent outburst of rage and/or psychopathy.
A: I'd have to be shithive maggots to try that ice cream flavor again.
B: Holy fuck, a dog just went shithive maggots on some old lady!
C1: This idea is completely shithive maggots.
C2: So, you'll do it, then?
C1: Fuck no.