neodređen

1. indefinite; unspecified
   Dobio sam ugovor na neodređeno vreme. — I got a permanent contract.
   Sastanak je odložen na neodređeno vreme. — The meeting has been postponed indefinitely.
2. vague; unclear
   Dao mi je neki neodređen odgovor. — He gave me some vague answer.
   Imam neodređen osećaj da nešto nije u redu. — I have a vague feeling something is wrong.
3. (in grammar) indefinite
   „Neko” i „nešto” su neodređene zamenice. — "Neko" and "nešto" are indefinite pronouns.

Ugovor na neodređeno (vreme) means a permanent, open-ended employment contract.