The phrase "inefficient use" refers to not using something in an effective or productive way. It means wasting or not getting the most out of a resource, time, energy, or any other valuable thing. Full definition
At the same time, currently existing biofuels, such as the ethanol produced from vast fields of corn, are a very inefficient use of energy and land. (greentechmedia.com)
It could transform the current very inefficient use of funds and dramatically change the way in which scientists do research. (scientificamerican.com)
Yet these things are at least easy to identify as inefficient uses of time. (foundersblock.com)