What does "leftism" mean?

Belief in the principles of left-wing politics.

Leftism

Common synonyms include: egalitarianism, left, left wing, left-wing politics, leftist analysis, leftist critique.

noun

noun ·3 syllables ·Rare ·Advanced level

Noun

1
Belief in the principles of left-wing politics. countable, uncountable
2
the ideology of the political left; belief in or support of the tenets of the political left wordnet

"Antisemitism is leftism for fools."

From left + -ism.