When you talk about something and never do it.

a big ass permanent upright constructions having a length much greater than the thickness and presenting a continuous surface except where pierced by doors, windows, illegal aliens etc.: used for shelter, protection, or privacy, to keep illegal aliens from entering the United States or to subdivide interior space, to support floors, roofs, or the like, to retain earth, to fence in an area, etc.

a big ass wall that the president decided to make so that he could stop mexicans from crossing the border

Something that sounds good, but is physically impossible.

A wall that is awesome. Separates us from the bad Mexies. Freedom.