Question: A technical writer wants to change a label of a table column. He says it is not clear. I, a usability expert, am against it. Who should have the last word?

Answer: 
Neither of you.

Instead, try to collect empirical data by doing research. Tie the results of your research to formal KPIs for the product's project. And be prepared to step back if the results don't go your way.
Test It.

Go and wander around the shops at lunchtime (ie do **not** ask people in your company - who will be too close to the jargon) and ask random people what the two alternate label words mean to them.