Body can understand
Molly uses the phrase "a body" colloquially to mean "an ordinary person," but in using this language to say that her husband can't explain things in ways she can understand she raises to a new level the novel's attention to experiencing the world in the flesh. If the example of Bloom shows how little Stephen lives in his own body, Molly's relentlessly corporeal anti-intellectuality goes Bloom one better.
Still trying to make sense of the unfamiliar word "metempsychosis" through familiar Anglo-Saxon physical actions—"that word met something with hoses in it"—she recalls how Bloom "came out with some jawbreakers about the incarnation" (i.e., reincarnation). His use of another synonym in Calypso, "the transmigration of souls," roused her indignation: "— O, rocks! she said. Tell us in plain words." Language, aided by Greek and Latin polysyllables, threatens to fly off into mists of abstraction just as souls threaten to fly out of their bodies. Perhaps it is no coincidence that, on the one other occasion when she uses the phrase "a body," Molly thinks of such decoupling as a vexation: "wouldnt that pester the soul out of a body." Souls belong in bodies, not floating free of them.