Picture staring at a herd of thirty zebras until your eyes give out. That's the situation here. Whether the animals stand side by side or nose to tail, the pattern stops holding still. The stripes blur into a "kaleidoscopic swirl" and seem to move "of their own accord," as if the pattern were alive and the animals were only its carrier.
The speaker doesn't seem alarmed by this. The short, dripping words "Drip. Slip. Slide" make the stripes feel liquid, passing from one body to the next or stretching over the whole crowd. By the end, the herd becomes a "cloud of communion," a single shared shape rather than thirty separate animals. The final image, something "savored, swallowed / like sun," turns the sight into something almost edible and warm.
The mood is dreamy, hypnotic and a little ecstatic. The title hints that the speaker knows this is a trick of the eyes, but enjoys giving in to it anyway.