EXCLUSIVE

Kelis to Nas Oh, My Lawyer's a Fat D**k?? Yours Just Screwed You!!!

When Nas and Kelis go to war, their lawyers jump right in also ... according to Kelis, who says Nas' attorney is calling hers a "dick."

Of course, the exes have an ongoing dispute over their child and she just filed docs, obtained by TMZ, which describe a deposition for which she recently sat. Things apparently got very heated ... and Kelis says Nas' lawyer called her attorney a "fattie" and a "dick."

Kelis' attorney, Navid Moshtael, says he's used to being called names -- he's a lawyer, after all -- but says this is the first time it's come from an "experienced attorney" in front of clients and on the record.

Imagine the transcriber's fingers flying during the argument.

Kelis says the name-calling is gonna cost Nas, because she says his team blew it when they stopped the depo to get childish. She doesn't sound like she's up for giving them a do-over, either.

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