The veteran defender also refused to apologize to Anton Ferdinand as he took the stand on the second day of his trial for an alleged racist slur hurled at the Queens Park Rangers player last October, which led to Terry being stripped of the England captaincy.
Terry and Ferdinand had traded insults after a disputed penalty call in the west London derby, with the Chelsea star goaded about an alleged affair with the former girlfriend of an ex-teammate.
"The truth of the matter is you are not a racist ... you used racial language that day because you snapped and it was instinctive," prosecutor Duncan Penny suggested to Terry. "You were fed up with people abusing you over the issue with your wife."
Terry, however, responded that "it was almost two years on and I had heard it a million times before."
"If I was going to snap, I would have snapped long before," he said.
The alleged affair led to Terry being stripped of the England captaincy by coach Fabio Capello ahead of the 2010 World Cup. Capello then restored Terry as captain but quit in February when the Football Association took away the armband from the defender against the Italian's wishes.
In Westminster Magistrates' Court, Terry hardly resembled the commanding figure seen just two weeks ago on the football pitch at the European Championship, where his orders boomed from the heart of defence for England.
Terry's voice was reduced to almost a whisper on Tuesday, as he stood with his hands clasped in front of him while being quizzed by Penny, as video footage of the alleged incident was replayed on screens in the court room.
Terry denied Penny's suggestion that his "blood was up" with Chelsea surprisingly losing 1-0 to QPR at Loftus Road.
Terry was pushed on whether he had ever considered apologizing to Ferdinand.
"Why would I apologize to Anton when he is the one who accused me?" Terry responded. "What I said was in response to what Anton said to me."
Terry told the court that he repeated an offensive term to Ferdinand during the confrontation because he believed the QPR player was accusing him of using it previously.
"I thought he was accusing me of calling him a black (expletive)," Terry said. "I was very angry and I was upset."
Penny, however, had said earlier in court that it was "plainly and inherently unlikely" Terry would decide to repeat the phrase with no surprise or incredulity.
Before Terry entered the witness box, his words were heard during the morning session from police statements and interviews taken last year.
In a police statement, Terry insisted the language he used was "responsive and not accusatory."
Defending his character to police, Terry highlighted his work helping to integrate a "multicultural group of players" at Chelsea and his long-standing support for the charity work of black former teammates Marcel Desailly and Didier Drogba.
"My commitment to the projects demonstrates I'm not racist," Terry told police.
Terry faces a maximum fine of 2,500 pounds ($3,900) if he becomes the first top football player in England convicted of racial abuse during a game.
Terry also repeatedly defended his character during disciplinary interviews last October with the English Football Association, which were presented to the court.
"I have been called a lot of things in my career and off the pitch but being racist is not one I am prepared to take at all," he said in those interviews.
"I'm not having anyone, let alone Anton, think that about me or anyone else," he added. "That's not my character ... I was taken aback by that. I have never been accused of that."
After the prosecution closed its case at lunchtime, Terry's legal team unsuccessfully tried to get the case thrown out.
Lawyer George Carter-Stephenson said Ferdinand "is not a reliable witness," claiming his evidence on Monday on the build-up to the confrontation with Terry was "misleading."
The verdict in the trial, which is expected to last five days, will be decided by chief magistrate Howard Riddle instead of a jury.
Rob Harris can be reached at http://twitter.com/RobHarris