Final answer:
The boldfaced word 'uproar' in the passage indicates the scale of noise and commotion by the gulls, hence 'size' is the most likely definition.
Step-by-step explanation:
The passage describes a hostile interaction between the narrator and a large number of gulls. The boldfaced word 'uproar' in this context refers to a loud and hectic situation, implying that there was a lot of noise and activity from the gulls as they reacted to the presence of the person mentioned. Given the choices provided, the most likely definition of 'uproar' would be size, as it indicates the scale or magnitude of the commotion caused by the gulls. The term does not pertain to the shape, part, or the height of the disturbance.