inefficient
inefficient adjective uk/ˌɪnɪˈfɪʃənt/ usInefficient people or things waste time, money, or effort, and do not achieve as much as they should.
неумелый, недейственный
an inefficient heating system inefficient ly adverb
неэффективно
inefficiency noun [ C,U ] uk/ˌɪnɪˈfɪʃənsi/ us
неспособность, недейственность