The speaker, who seems to be a woman, imagines breasts as watchful, almost godlike presences. They follow her from mirrors and curtains, and they make her feel her own are lacking, unable to "shoot sweetness" at a hungry world. The images grow strange and playful: breasts become crockery, solar flares, bells ringing backwards. "Wholly holy" puns on how a body part can be both complete and sacred.
Then the tone turns wry. If these eyes ever blinked, "we would all disappear," so they must be covered up, supposedly to protect men's dignity, since men "tremble like virgins" when they see them. The speaker sounds amused by this fuss, and a little critical of it.
The last lines drop the joking and state the point plainly: breasts are "the most human thing." The mood moves from teasing and surreal to quietly tender. The poem suggests that all the awe, fear and shame around breasts hides something simple, which is that they belong to our shared humanity.