Mom warned me not to back-talk her, or I would be sent to stand in the corner.

back-talk 是由 back（后面）和 talk（说话）组成的复合动词，字面意思是"在后面说话"，引申为"顶嘴、回嘴"的意思。back-talk 指不礼貌地反驳长辈或权威人士的话。