1
general::
Discuss fully, especially to resolve a problem, as in We'll just have to thrash out our ideas about where to go on vacation. [Late 1800s]
American Heritage Idioms
2
general::
Phrase(s): thrash something out
Fig. to discuss something thoroughly and solve any problems. • The committee took hours to thrash the whole matter out. • John and Anne thrashed out the reasons for their constant disagreements.
McGrawhill's American Idioms And Phrasal Verbs