Final answer:
The bold word in the sentence is 'vastness' and it refers to the immense size or scale of the world.
Step-by-step explanation:
The bold word in the given sentence is 'vastness'.
In the context of the poem, the word 'vastness' refers to the immense size or scale of the world.
This is evident from the following line in the poem: 'And I throbbed with a burning desire / To travel this immensity.' The word 'immensity' further emphasizes the idea of something very large, which relates to the meaning of 'vastness'.
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