lack·lus·ter (US) or Brit lack·lus·tre 
/ˈlækˌlʌstɚ/ adjective
/ˈlækˌlʌstɚ/ adjective [more lackluster; most lackluster] : lacking excitement or interest
▪ a lackluster [=dull, mediocre] performance ▪ His writing can be lackluster [=uninspired] at times.
▪ a lackluster [=dull, mediocre] performance ▪ His writing can be lackluster [=uninspired] at times.
