A top Westpac trader has claimed that when he said "I'm going to f--k the rate set" he really meant other banks could be manipulating one of Australia's key interest rates and was not referring to his own actions in rigging the rate.

Under a withering cross examination at the Federal Court on Friday, Westpac's Colin "the Rat" Roden repeatedly denied he talked openly with his colleague about manipulating the bank bill swap rate to benefit the bank and to the detriment of its customers and rival banks.

Mr Roden's response that his use of the phrase "I'm going to f--k the rate set" did not refer to his own trading activities appeared to concern Justice Jonathan Beach who has been hearing the landmark case.

"It's a verb, it's an active verb, and you're going to achieve it?" Justice Beach said to Mr Roden following the explanation.