disappointingly unsuccessful; "disappointed expectations and thwarted ambitions"; "their foiled attempt to capture Calais"; "many frustrated poets end as pipe-smoking teachers"; "his best efforts were thwarted"
If you are disappointed, you are rather sad because something has not happened or because something is not as good as you had hoped. Castle-hunters won't be disappointed with the Isle of Man I was disappointed that Kluge was not there I was disappointed to see the lack of coverage afforded to this event
If you are disappointed in someone, you are rather sad because they have not behaved as well as you expected them to. You should have accepted that. I'm disappointed in you. unhappy because something you hoped for did not happen, or because someone or something was not as good as you expected