What term describes a masonry column that projects from one or both faces of a wall?

The term that describes a masonry column projecting from one or both faces of a wall is "pilaster." A pilaster serves both functional and aesthetic purposes. Functionally, it can help support the wall structure, much like a column, but it is designed to be integrated into the wall rather than standing independently. Aesthetically, pilasters enhance the architectural design and visual appeal of a building.

In contrast to other options, a colonnade refers to a series of columns that support a roof or a series of arches, but it is not specifically about an element projecting from a wall. The term "columnar" generally describes something relating to or shaped like a column, without the specific implication of being attached to a wall. A post typically refers to a vertical support that is used in various structural contexts but does not inherently imply a connection to a wall in the way a pilaster does.