not doing a job well and not making the best use of time, money, energy, etc. an inefficient heating system inefficient government an extremely inefficient secretary inefficient use of time and energy opposite efficientExtra examples an economically inefficient system The boss thinks the new secretary is inefficient. The regime was both inefficient and corrupt. The system is inherently inefficient. They continued to prop up inefficient state enterprises. This method of data storage is an inefficient use of memory.