WordWeb Online

1. Of superficial relevance if any
   "a digressive allusion to the day of the week";
   - tangential
    
2. (of e.g. speech and writing) tending to depart from the main point or cover a wide range of subjects
   "amusingly digressive with satirical thrusts at women's fashions among other things";
   - discursive, excursive, rambling

See also: beside the point, indirect, irrelevant