What is Quay?

Legal Definition
Estates. A wharf at which to load or land goods, sometimes spelled key.

2. In its enlarged sense the word quay, means the whole space between the first row of houses of a city, and the sea or river 5 L. R. 152, 215. So much of the quay as is requisite for the public use of loading and unloading vessels, is public property, and cannot be appropriated to private use, but the rest may be, private property. Id. 201.
-- Bouviers Law Dictionary
Legal Definition
A wharf for the loading or unloading of goods carried in ships. This word is sometimes spelled "key." The popular and commercial signification of the word "quay" involves the notion of a space of ground appropriated to the public use ; such use as the convenience of commerce requires. New Orleans v. U. S., 10 Pet. 662, 715, 9 In Eld. 573.
-- Black's Law Dictionary