zategnuti

1. (of a rope, string, screw) to tighten; to pull taut
   Zategni konopac da šator ne padne. — Pull the rope tight so the tent doesn't fall.
   Majstor je zategao sve šrafove na vratima. — The repairman tightened all the screws on the door.
2. (of skin, muscles, the body) to firm up; to tone
   Posle tri meseca vežbanja zategla je stomak. — After three months of exercise she toned her stomach.
3. (of relations, a situation) to strain; to make tense
   Taj incident je dodatno zategao odnose između dve zemlje. — That incident further strained relations between the two countries.

The imperfective is zatezati; the participle zategnut often means "tense": zategnuti odnosi.