Los Angeles (CNN Business) "Disgusting." That's the word Vernon Unsworth used to describe how he felt when his attorney asked him what it was like to be "branded a pedophile" after Tesla CEO Elon Musk called him "pedo guy" in a tweet.

Unsworth, a caver from the UK who was part of the rescue team that saved 12 boys and their soccer coach from a cave in Thailand last summer, took the stand in a Los Angeles courtroom on Wednesday for a defamation lawsuit he brought against Musk for the tweet.

During the trial's first day on Tuesday, Musk testified that "pedo guy" was meant to be an insult, not a statement of fact. Musk reiterated that opinion the next day to Unsworth's attorney L. Lin Wood, saying, "I want to be clear I did not accuse Mr. Unsworth of being a pedophile. No one took it that way."

But in the same courtroom on Wednesday, Unsworth said he took Musk's tweet literally and got choked up when Wood asked him how it felt.

"It feels very raw," Unsworth said. "I feel humiliated, ashamed, dirty. Effectively from day one I was given a life sentence without parole."

In September 2018, Unsworth sued Musk for defamation, seeking punitive and compensatory damages. Unsworth claims Musk's tweets harmed him by associating his name with the act of pedophilia.

The dramatic rescue efforts gained international attention last summer after heavy rain water trapped the boys and their soccer coach in a cave for more than two weeks. Musk involved himself in the effort by creating mini submarine to save the boys. His "pedo guy" tweet came after he saw a CNN interview in which Unsworth said Musk "can stick his submarine where it hurts." Musk's tweet was indeed widely covered by the media.

"I'm not sure of how many times it was repeated, but it was essentially my name was being tied to being a pedophile. I find it hard to read the word let alone talk about it," Unsworth said.

Plaintiff, British cave expert Vernon Unsworth, right, arrives at U.S. District Court Wednesday, Dec. 4, 2019, in Los Angeles. Tesla CEO Elon Musk is going on trial for his troublesome tweets in a case pitting the billionaire against the British diver he allegedly dubbed a pedophile.

But Musk and his legal team are vying to prove to the jury that "pedo guy" is a colloquialism and Musk used it as an insult after Unsworth provoked him.

When Musk's attorney Alex Spiro asked him what about Unsworth "upset" him, Musk said, "There were a lot of people who worked day and night to be helpful even though the probabilities was low. He denigrated their efforts in a way that was completely inappropriate and wrong."

"It was extremely rude," Musk said. "It was an unprovoked attack on my team with false statements. It was rude and insulting so I insulted him back, regrettably, obviously."

One of those "false statements" Musk cited was when Unsworth called his effort a "PR stunt." In court on Wednesday, Spiro showed emails between Richard Stanton, one of the divers in the Thai cave rescue, and Musk communicating about how to best build the mini submarine. For example, Musk asked if it should be rigid or flexible, to which Stanton said rigid.

Stanton testified as a witness on Wednesday, saying he did provide "limited input" to Musk on his submarine. While the defense tried to get Stanton to downplay Unsworth's role in the rescue, Stanton repeatedly gave credit to Unsworth saying he "had the best knowledge of the cave."

After the testimony and outside the courtroom, Stanton told a group of reporters that he believed Musk's plan would not have worked.

Wood presented dozens of tweets Musk sent during the time he was building the submarine in an attempt to show the jury that Musk involved himself in the rescue mission to gain media attention. Asked why he tweeted out a video of the mini submarine being tested, Musk said, "I frequently solicit feedback from the public on many things, the Tesla design, some of the rocket stuff. There are some smart people out there, and they have some good feedback."

Musk's legal team referred to "pedo guy" as a colloquialism and asked Unsworth about his own use of colloquialisms like the British phrase "lost the plot" and 555, which means "hahaha" in Thai texting. The defendant's lawyer also tried to show that Unsworth did not actually experience "emotional distress" by reading out loud to the courtroom some texts between Unsworth and his friend Thanet Natisri.

Jared Birchall, the head of Musk's family office, testified on Wednesday about his role in hiring a private investigator to look into Unsworth.

Musk also told the jury about his net worth, admitting he doesn't "have a lot of cash." When Wood asked if Musk was worth about $20 billion, Musk said, "I think my SpaceX and Tesla stock may amount to something like that."

Three more witnesses -- Unsworth's ex-wife Vanessa Unsworth, professor Bernard "Jim" Jansen and Musk associate Sam Teller -- are expected to testify on Thursday.