napeti

1. to tighten; to stretch taut
   Napeo je konopac između dva drveta. — He stretched the rope tight between two trees.
   Strelac je napeo luk i nanišanio. — The archer drew the bow and took aim.
2. (of muscles) to tense; to flex
   Napni stomak i zadrži deset sekundi. — Tense your stomach and hold for ten seconds.
3. (napeti se) to strain; to exert oneself
   Napeo se iz sve snage, ali ormar se nije pomerio. — He strained with all his might, but the wardrobe didn't budge.

The imperfective counterpart is napinjati.