Thrash out
Definition 1 of 1
Pro Tip 1/3Resolve Conflict
Use 'thrash out' when people need to resolve disagreements or differences through discussion. 
The committee will thrash out the budget discrepancies tomorrow.
Pro Tip 2/3Detailed Discussion
'Thrash out' implies going into great detail, not just a casual conversation. 
We spent hours trying to thrash out the terms of the contract.
Pro Tip 3/3Work-Towards Agreement
The phrase is often used when the goal is to agree on something important. 
They need to thrash out who takes ownership of the project.