As a result, I took my second monitor and mounted it in portrait mode, and to be honest, I don't think I could ever go back.

A computer monitor that is taller than it is wide. Most portrait monitors are actually landscape monitors that can be swiveled into a portrait orientation. See landscape monitor and portrait.

some monitors can be swiveled into portrait mode. See portrait monitor and landscape. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction requires permission.