Made muscles tight and stiff, usually from stress, fear, or anticipation; became rigid or tight.
From 'tense,' which comes from Latin 'tensus' (stretched or tight), the past participle of 'tendere.' The adjective became a verb in English to describe the action of becoming tense.
Your body tensing up is an ancient survival mechanism called the 'fight-or-flight response'—your muscles tighten to prepare for action! Animals do this too, which is why cats arch their backs when scared.
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