The word 'unwasteful' refers to something that is not wasteful or extravagant. The antonyms for this word would be wasteful, extravagant, prodigal or spend-thrift. These words convey the idea of spending or using things indiscriminately or without proper care. A person or business that is wasteful will spend money carelessly or use resources in a way that is not sustainable or efficient. Being mindful of one's resources and how they are used is an important aspect of being responsible, and the opposite of being wasteful. So, it's good to be mindful of how we use our resources to live our life economically.