Having no useful purpose
Incapable of being used or availed of to advantage
Having no useful result
Not having the desired effect
As strong as he was, it would be useless to resist.
The symbols were useless to him.
It's useless to dwell on what might've been.
She suggested he take the cell phone but then remembered it was useless in the high mountains.
A piece of cotton wool soaked in strong carbolic acid will relieve the pain of dental caries, but is useless in other forms of toothache.