expression, ichidan verb
interrupt with a jeer; heckle
Used when someone cuts into a speech, performance, or conversation with a mocking or critical remark. The expression originates from the practice of throwing a half-sized tatami mat (半畳) onto a stage to show disapproval.
演説中に野次馬が半畳を入れた。
A heckler interrupted the speech with a jeer.
野次る is a general verb for jeering or heckling, while 半畳を入れる specifically implies a cutting, critical interruption, often with a historical or theatrical nuance.
Literally 'to throw in a half tatami mat'. Historically, audience members would throw a half-sized tatami mat onto the stage to express disapproval or to interrupt a performance. The exact historical derivation is uncertain, but the phrase is conventionally associated with this practice.