The word "declaim" means to recite or pronounce something in a dramatic or vehement manner. The antonyms for declaim are words that indicate the opposite of declaiming. These words include whisper, murmur, mumble, speak softly, and remain silent. Whisper implies speaking softly and quietly, while murmur refers to the soft and indistinct sound of voice. Mumble is another antonym for declaim which means to speak in a low voice with insufficient articulation. Speak softly means speaking in a low or soft-toned voice. Remaining silent is the opposite of declaiming since it means not speaking or making any sound.