Final answer:
The word 'rampart' in the given context means an embankment built around a space for defensive purposes, serving as a protective barrier.
Step-by-step explanation:
In the given context, the word 'rampart' refers to option 4: an embankment built around a space for defensive purposes.
In the sentence, it describes a structure that separates the beach and the ocean from the street, providing a sense of protection to the adjacent area. It is likely a high, sturdy barrier where markets take place on Saturday afternoons. This type of structure has historical significance as it was often used in the past to protect towns and settlements from potential invaders or the forces of nature.