tense_up
1. [ verb ] become tense or tenser
Synonyms: tense
Examples:

"He tensed up when he saw his opponent enter the room"

Related terms: relax change_state tension
2. [ verb ] make tense and uneasy or nervous or anxious;
Synonyms: strain tense
Related terms: relax relax relax affect stretch crick tension tense
Similar spelling:   tennis_pro
  tennis_ball