Definition from Wiktionary, the free dictionary
soapbox (plural soapboxes)
- (literally) A crate for packing soap, or, by extension, any inexpensive crude platform raised above the surrounding level to give prominence to the person on it, especially when used for speeches.
- The madman obtained a soapbox which he stood on at the corner of Broadway and Wall street, to shout out his prophesy of the end of the world.
- (figuratively, idiomatic) A talk about one's pet topic (or the topic itself), especially when only tangentially relevant to an ongoing discussion.
- He's been on his soapbox all day about the new football coach.
- a soapbox car
- To give a speech from (or as if from) a soapbox.