very difficult; severely testing stamina or resolution; "a rugged competitive examination"; "the rugged conditions of frontier life"; "the competition was tough"; "it's a tough life"; "it was a tough job"
feeling physical discomfort or pain (`tough' is occasionally used colloquially for `bad'); "my throat feels bad"; "she felt bad all over"; "he was feeling tough after a restless night"
making great mental demands; hard to comprehend or solve or believe; "a baffling problem"; "I faced the knotty problem of what to have for breakfast"; "a problematic situation at home"