街宣車
がいせんしゃ sound truck (used for campaigning, advertising or propaganda); loudspeaker van
Why it means this
街宣 (street announcing — from 街頭宣伝) + 車 (a vehicle) — a loudspeaker van, used for campaigning or by right-wing activists.
Breakdown
Each character links to its full entry — origin story, stroke order, and readings.