[decimalenough]

I always thought a McMansion was primarily defined by cramming too much house into a small plot.

An actual mansion is a mansion in large part because the grand building is set off by a vast expanse of lawns and gardens around it. A suburban McMansion dispenses with that and just crams the maximum amount of Roman columns, crenellated turrets and whatever else the designer thinks looks impressive into a cancerous-lookimg building that extends right out to the property line.