1. Antonyms for Blathering include reticent, taciturn, reserved, uncommunicative, tight-lipped, closemouthed, laconic, quiet, silent and monosyllabic

2. Tongue tied Synonyms and related words: Anaudic, aphasic, aphonic, breathless, brief, brusque, close, close-tongued, closemouthed, concise, curt, dumb, dumbfounded

3. 43 Moby Thesaurus words for "speechless": Anaudic, aphasic, aphonic, breathless, brief, brusque, close, close-tongued, closemouthed, concise, curt, dazed, dumb