Its dictionary entry says it is “the theory that an increasing consumption of goods is economically desirable.”
If we go deeper, consumerism is part of a social and economic line of thinking that believes growing production and consumption are the only ways to generate wealth and ensure prosperity.
On paper, producing and buying more does lead to the circulation of money, but it so in a disproportionate way.
Consumerism isn’t compatible with sustainability. From an environmental point of view, it’s based on overproduction and overconsumption, which contribute to resource depletion and waste generation.