DIGRESSIVE
digressive, discursive, excursive, rambling
(adjective) (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”; “a rambling discursive book”; “his excursive remarks”; “a rambling speech about this and that”
digressive, tangential
(adjective) of superficial relevance if any; “a digressive allusion to the day of the week”; “a tangential remark”
Source: WordNet® 3.1
Etymology
Adjective
digressive (comparative more digressive, superlative most digressive)
Marked by digression; rambling
Source: Wiktionary
Di*gress"ive, a. Etym: [Cf. F. digressif.]
Definition: Departing from the main subject; partaking of the nature of
digression. Johnson.
Source: Webster’s Unabridged Dictionary 1913 Edition