Xavien Howard is firing back at his accuser in new court documents, obtained by TMZ Sports ... calling the woman "a scorned ex-lover" -- and insisting her STD lawsuit against him is "the epitome of a shakedown."
The Miami Dolphins star filed the docs on Friday -- one day after the woman, who filed her suit anonymously as Jane Doe, claimed he negligently gave her genital herpes.
In the documents, Howard argued the woman's suit should be thrown out ... and he says the woman has stalked him, threatened him with violence, and tried to extort him for cash.
In the docs, Howard claims he has text message proof that showed the woman is "nothing more than a scorned ex-lover who has elected to prey on [Howard's] public status for the purpose of obtaining a financial windfall without right or claim."
The cornerback even included texts that he says show the woman calling him curse words ... before threatening to "come to your job tomorro and cause a whole scene."
For her part, the woman filed court docs of her own on Monday, saying she should be allowed to proceed with the lawsuit under the Doe pseudonym ... insisting the circumstances have already caused her "embarrassment, humiliation, and psychological trauma" that would be worsened if she had to reveal her name.