From Longman Dictionary of Contemporary Englishthrash something ↔ out phrasal verbDISCUSSto discuss something thoroughly with someone until you find an answer, reach an agreement, or decide on something We still have to get together and thrash out the details. → thrash→ See Verb table
Examples from the Corpus
thrash out• Why hadn't they gone into all this at the time, really thrashed it out?• After a fortnight drying out, the sheaves will be stacked in a rick ready for thrashing to separate out the grain. 