trgnuti

1. (+ acc.) to jerk; to pull; to tug
   Trgnuo je ruku sa vrelog šporeta. — He jerked his hand away from the hot stove.
   Trgni jače, vrata su zaglavljena. — Pull harder, the door is stuck.
2. (trgnuti se) to flinch; to start
   Trgla se kad je zazvonio telefon. — She flinched when the phone rang.
   Trgao sam se iz sna oko tri. — I woke with a start around three.
3. (trgnuti se) to pull oneself together; to snap out of it
   Trgni se, nije kraj sveta! — Pull yourself together, it's not the end of the world!
4. (from sleep, thoughts) to jolt; to startle
   Zvono na vratima ju je trglo iz misli. — The doorbell jolted her out of her thoughts.
5. colloq. (of a drink) to down; to knock back
   Hajde da trgnemo po jednu pre večere. — Let's knock back one each before dinner.

The imperfective is trzati; trgnuti se means both 'to flinch' and 'to pull oneself together'.