What is a white elephant? Symbolize the story?
One question per day, please.
According to Enotes:
A white elephant is an idiom for a valuable possession of which its owner cannot dispose and whose cost (particularly cost of upkeep) is out of proportion to its usefulness or worth.
So, the white elephant is the unborn baby that the couple is discussing. The woman, Jig, is obviously the owner and her unwillingness to dispose of the baby is clear, though she does not expressly denounce the idea. The much subtext and unstated tension between the couple. The unsaid and unseen are as important and symbolic as the said and seen.
According to the wonderful Enotes critical essay "Symbolism is 'Hills Like White Elephant,'" by Lewis E. Weeks:
Emphasis by position and repetition clearly suggests the importance Hemingway attached to the comparison. Besides the reference in the title, there are, within this very short three-page story, two references to the whiteness of the hills and four to them as white elephants, although one of these suggests that the hills do not look like white elephants but only have their coloring.
On first reading the title, one assumes the comparison may merely be to the color and to the rounded contour of the hills that constitute part of the setting, a quite literal reference. This impression is reinforced by the first sentence, the subject of which is ‘‘long and white’’ hills. The second time they are mentioned, they are contrasted with the countryside, which is brown and dry, suggestive of the limitations and aridity of the relationship of the man and woman, which begins to unfold and which is the basis of the conflict and the meaning of the story.