Bill Cosby is firing back at seven women who are suing him for defamation, accusing them of making false accusations of sexual misconduct for financial gain.

Cosby filed counterclaims in federal court Monday, alleging the women made "malicious, opportunistic, and false and defamatory accusations" of sexual misconduct against him. Cosby is seeking unspecified monetary damages.

The women claim Cosby defamed them by allowing his representatives to brand them as liars after they went public with allegations of rape and other sexual misconduct dating back decades.

In his counterclaim, Cosby says the women have "engaged in a campaign to assassinate" his reputation and character. He says their campaign is "nothing more than an opportunistic attempt to extract financial gain from him."

The women suing Cosby in Massachusetts are among approximately 50 who have accused the comedian of rape or unwanted sexual contact.

News of Cosby's counterclaim comes on the heels of Boston University's announcement Monday that trustees have voted to revoke an honorary Doctor of Humane Letters degree awarded to Cosby during its May 2014 commencement.

The university joins several other schools around the country that have rescinded honorary degrees awarded to Cosby, saying in a statement that the entertainer's treatment of women "brought significant and lasting discredit upon himself" and was inconsistent with the school's values.

BU cited Cosby's own sworn deposition, in which he acknowledged offering quaaludes to women before sexual encounters, as a factor in its decision.