1. (of e.g. speech and writing) tending to depart from the main point or cover a wide range of subjects

e.g. amusingly digressive with satirical thrusts at women's fashions among other things
a rambling discursive book
his excursive remarks
a rambling speech about this and that

Synonym: discursiveexcursiverambling

2. of superficial relevance if any

e.g. a digressive allusion to the day of the week
a tangential remark

Synonym: tangential