The definition of Antisemitism, as put forth by the International Holocaust Remembrance Alliance (IHRA):

“Antisemitism is a certain perception of Jews, which may be expressed as hatred toward Jews. Rhetorical and physical manifestations of antisemitism are directed toward Jewish or non-Jewish individuals and/or their property, toward Jewish community institutions and religious facilities.”

Britannica offers a broader definition of Antisemitism, "hostility toward or discrimination against Jews as a religious or racial group", and also provides information on the history of Anti-Semitism | Britannica

The US Government adopted the European Monitoring Center on Racism and Xenophobia's working definition of Antisemitism in 2010. "Anti-Semitism is a certain perception of Jews, which may be expressed as hatred toward Jews. Rhetorical and physical manifestations of anti-Semitism are directed toward Jewish or non-Jewish individuals and/or their property, toward Jewish community institutions and religious facilities."  This definition was expanded to include the IRHA's definition in 2016. Most recently, in May 2023, the U.S. government released a comprehensive plan to counter Antisemitism which includes measures by federal agencies and calls to action focused on four pillars: raising awareness, improving security, reversing normalization and building intergroup solidarity. To read more about it you can read here: U.S.-National-Strategy-to-Counter-Antisemitism.pdf