Mumblingly is an adverb used to describe something that is said in a low, unclear, or indistinct manner. If you're looking to mix up your descriptive vocabulary, here are a few synonyms for mumblingly: indistinctly, inaudibly, muttering, murmuring, softly, quietly, sotto voce, under one's breath, hushedly, unintelligibly, incomprehensibly, garbled, muffled, faintly, meekly, hesitantly. Each of these words offers a slightly different nuance to the meaning of mumblingly, allowing you to choose the perfect word to convey the exact mood or tone you're aiming for in your writing or speech.