uozbiljiti

1. (uozbiljiti se) to become serious; to turn serious
   Kad je čuo vest, odmah se uozbiljio. — When he heard the news, he immediately turned serious.
2. (uozbiljiti se, of a person) to settle down; to grow up
   Posle rođenja sina, konačno se uozbiljio. — After his son was born, he finally settled down.
3. (uozbiljiti se, of a situation) to get serious
   Stvari su se uozbiljile kad je stigla policija. — Things got serious when the police arrived.
4. (+ acc.) to make serious; to sober
   Ta vest ga je odmah uozbiljila. — That news sobered him up at once.

Mostly used with se; the imperfective is uozbiljavati se.