Green’s Dictionary of Slang

1. to act crazily, aggressively, wildly; thus illing n.

1988		G. Tate ‘Public Enemy’ in Flyboy in the Buttermilk (1992) 121: The dominant activity was milling and chilling, not illin’.
1988		Ice-T ‘Drama’ 🎵 Then my boy started illin’, talkin’ and tellin’.

2. to do something very well.

1992

L. Stavsky et al. A2Z.