What does rule Sec 2.17(3) mean in a frame?

Section 2.17 Snookered

(e) The cue-ball cannot be snookered by a cushion. If the curved face of a cushion obstructs the cue-ball and is closer to the cue-ball than any obstructing ball not on, the cue-ball is not snookered.

Is this just a definition, i.e. the cue ball is angled, rather than snookered?

What does rule Sec 2.17(3) mean in a frame?