These are British English definitions of the word:
http://oxforddictionaries.com/definition/english/discursive?q=discursive
discursive
adjective
1 digressing from subject to subject:
"students often write dull, second-hand, discursive prose"
(of a style of speech or writing) fluent and expansive:
"the short story is concentrated, whereas the novel is
discursive"
http://www.collinsdictionary.com/dictionary/english/discursive
1 passing from one topic to another, usually in an unmethodical way;
digressive
http://dictionary.cambridge.org/dictionary/british/discursive
FORMAL talking about or dealing with subjects that are only slightly
connected with the main subject for longer than necessary:
"a discursive writer/speech"
Many discussions in this newsgroup are discursive. We wander off-topic.
There other senses of the word "discursive"
involving discussion: "a discursive essay"
and the archaic sense in Philosophy:
proceeding by argument or reasoning rather than by intuition.
This is from Webster's New World College Dictionary (US):
http://www.yourdictionary.com/discursive
1. wandering from one topic to another; skimming over many
apparently unconnected subjects; rambling; desultory; digressive
2. based on the conscious use of reasoning rather than on intuition
--
Peter Duncanson, UK
(in alt.english.usage)