Final answer:
In a Boston Matrix, a product in a high-growth market with underperforming sales is known as a problem child. These products face strategic decisions like investment or divestment due to their low market share and high cash consumption.
Step-by-step explanation:
The category in a Boston Matrix that describes a product in a high-growth market but is not meeting market growth sales expectations is known as a problem child or a question mark. These products consume a lot of cash but generate little in return due to their low market share in a rapidly growing market. The main strategic options for a problem child include increased investment to gain market share, repositioning to improve growth prospects, or divesting if deemed unfit for the long-term strategy of the company.