齐声 (qí shēng) literally combines 齐 (qí), meaning 'together' or 'in unison', and 声 (shēng), meaning 'voice' or 'sound'. Together, it describes the act of multiple people speaking, singing, or shouting at the exact same time — with coordination and unity. It emphasizes collective vocal action rather than mere simultaneity; the emphasis is on harmony and shared intention.

This term is commonly used in contexts like classrooms, rallies, ceremonies, sports events, or choir rehearsals — anywhere group vocal participation occurs intentionally. While it can occasionally describe non-human sounds (e.g., birds chirping together), its primary usage centers on human group behavior. It functions as an adverb modifying verbs like 喊 (shout), 唱 (sing), or 说 (say), and rarely appears as a noun or adjective. It carries a neutral-to-positive connotation, suggesting order, enthusiasm, or solidarity.