English to English

verb (v)

• become tense, nervous, or uneasy(verb.body)

  Synonym:
  tense
  Antonym:
  decompress, loosen up, relax, slow down, unbend, unwind
  

  source: wordnet30
• cause to be tense and uneasy or nervous or anxious(verb.body)

  Synonym:
  strain, tense
  Antonym:
  loosen up, make relaxed, relax, unlax, unstrain, unwind
  

  source: wordnet30