Death here is imagined as a place, and a strangely huge one. The grave in the poem is "an infinite room," which turns the usual picture of a small, cramped hole in the ground into something vast and empty. The body that falls into it is "finest," but also "overthrown" and "irregular," as if it has been toppled from whatever order or dignity it once had. The title, "Finite," sits in sharp contrast to that endlessness: a limited life drops into a space with no limit.
The last two lines are the most unsettling. "The no body to know / how to pass" suggests that once the body is gone, nobody is left who understands how to go through death, or perhaps that nobody can teach it. The speaker sounds quiet and stunned rather than angry. The mood is hushed and dizzying, a bit like looking down a long drop and realizing you can't see the bottom. The poem doesn't comfort the reader. It simply leaves us standing at the edge, with the words breaking apart as the body does.