Green’s Dictionary of Slang

nibshit adj.

[nibshit n.2 ]

1. meddlesome, interfering.

G. Wolff Providence 165: Skippy was pissed at the hassle, the ceaseless duplicate-triplicate-quadruplicate-sign-here bureaucratic nibshit regulations.
R. Ford Lay of the Land 335: To me, it’s a worse signal that anybody would ever worry about these things than that he/she can’t remember every little bit of nibshit minutiae.

2. stupid.

G. Wolf Final Club 71: There was the Minnesotan with his nibshit nickname — Jamie — wearing a monocle attached by a black silk ribbon to his waistcoat.