tense up
    v 1: become tense, nervous, or uneasy; "He tensed up when he saw
         his opponent enter the room" [syn: tense, tense up]
         [ant: decompress, loosen up, relax, slow down,
         unbend, unwind]
    2: cause to be tense and uneasy or nervous or anxious; "he got a
       phone call from his lawyer that tensed him up" [syn: tense,
       strain, tense up] [ant: loosen up, make relaxed,
       relax, unlax, unstrain, unwind]