Main entry: elusive, tough, baffling, problematic, problematical, knotty
Definition: making great mental demands; hard to comprehend or solve or believe
Usage: a baffling problem; I faced the knotty problem of what to have for breakfast; a problematic situation at home
Main entry: problematic, problematical, debatable
Definition: open to doubt or debate
Usage: If you ever get married, which seems to be extremely problematic