It means the invention is capable of improving a commercial product.

One of the criteria of patentability also referred to as "utility". For the purposes of written opinions of the International Searching Authority and international preliminary report [..]

is one of the three basic patentability requirements under the European Patent Convention. An invention will be considered capable of industrial application if it can be made or used in any kind of industry. This requirement is to be understood in a broad sense: it includes for instance applications in the agricultural field. See also: Inventive st [..]

A requirement that an invention be “susceptible” of some industrial …

In the US, an invention must be novel, useful and not obvious to be patentable. In PCT practice and in many foreign countries, the equivalent standards are novelty, industrial applicability and invent [..]