This poem of Emily Dickinson's seeks to describe a mental experience. Critics argue that the poem uses the image of the progression of a funeral to trace the stages of some kind of mental breakdown. The last stanza indicates how the coffin is placed on planks set over by a grave and then one of the planks breaks and the coffin drops down into the grave. suggesting perhaps the mind's final plunge into the abyss of despair.
The final separation of the speaker from the world comes with this breaking of the plank and the loss of reason; there is now nothing left to support her, no rational thought at all. The whole poem moves towards this moment of falling into an abyss, and even the rhyme scheme can be said to emphasise this movement. The first four stanzas use exact rhyme, whereas, in the final stanza, as reason breaks down and the mind plunges into despair, the established rhyme pattern simultanously breaks down with the sudden use of slant rhyme in "down" and "then".
The "World" that the speaker "hits" is one where she "Finished knowing - then -". It has been suggested that after breaking through the bounds of reason the speaker finished by suffering a complete loss of all thought, understanding and knowledge. Note how the dash seems to emphasise this meaning - we are not given a neat finish - the dash leaves something hanging as indeed the speaker is in her state of unknowing.
The "World" then seems to suggest some kind of symbolic abyss of despair, depression, or even madness, that is the result of the "Funeral" felt in the speaker's brain in the first stanza.