What is the meaning of Soapbox?

A crate for packing soap.

A small platform, being or resembling a literal soapbox, on which a person stands in order to give an impromptu speech or espouse his or her views.

A platform or outlet, such as a media platform, that a person uses to express his or her opinions.

A figurative means of talking repeatedly or at length about one's opinions on one's pet topic.

The topic itself.

A soapbox car.

To give a speech from (or as if from) a soapbox.

Source: wiktionary.org