The wall symbolizes the social boundaries that we as humans build. An example of a wall would be, "I'm not going to talk to my neighbor because it might be awkward." The poem is about how, even though some of us would love to see the 'walls' torn down, we still continue to recognize and enforce these social boundaries.

Symbol

"SOMETHING there is that doesn't love a wall,
That sends the frozen-ground-swell under it,"
(Ln. 1-2)