ekstra

1. colloq. great; excellent
   Film je bio stvarno ekstra. — The film was really great.
   Imaju ekstra kafu u tom kafiću. — That café has excellent coffee.
2. extra; additional
   Za ekstra prtljag plaća se posebno. — You pay separately for extra luggage.
   Treba mi ekstra sat da završim posao. — I need an extra hour to finish the job.

3. (before an adjective) extra; exceptionally
   Naručio sam ekstra ljutu picu. — I ordered an extra spicy pizza.
   Ovaj telefon je ekstra tanak. — This phone is extra thin.
4. colloq. great; brilliantly
   Na moru smo se proveli ekstra. — We had a great time at the seaside.
5. extra; additionally
   Doručak se plaća ekstra. — Breakfast costs extra.

The word does not decline: ekstra film, ekstra kafa, ekstra ljudi.