The Federal Bureau of Investigation is altering its long-acting definition of rape to include men and people who do not physically resist as victims.
The new definition will increase the number of people counted as rape victims in FBI statistics, but it will not change federal or state laws.
Earlier, the FBI defined rape as 'the carnal knowledge of a female, forcibly and against her will'.
The new definition removes the reference to females and says rape is "the penetration, no matter how slight, of the vagina or anus with any body part or object" without the consent of the victim, The BBC reports.
Also specified is "oral penetration by a sex organ of another person" without consent.
Vice-President Joe Biden, who raised the issue last July at a Cabinet meeting, called the change a victory for those "whose suffering has gone unaccounted for over 80 years".
"We can't solve it unless we know the full extent of it," Biden said.