1. the ability to make good judgements and quick decisions in business
the business is struggling because the boss has no commercial acumen
Generally speaking, somebody with 'commercial acumen' makes good decisions, recognizes opportunities and has a clear understanding of how an organization or market operates. This ability can be acquired through considered analysis or as a result of something instinctive, like a talent. It is almost always used in a professional context. A phrase with a similar meaning is 'business savvy.'