Unable to express one's full meaning in words; words fail to convey the intended message.
面对突如其来的变故，他心中思绪万千，却激动得辞不意逮，一时语塞。
Faced with the sudden turn of events, his mind was filled with a myriad of thoughts, yet he was so agitated that words failed him, leaving him speechless for a moment.
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