Quote Originally Posted by синичка
But yes, I think I would say "to have a snack" is informal, so that means I can use перекусить if I'd use "to have a snack" in English?
Yes, you are quite right. "Перекусить" is definitely your word in such case.
My dictionary confirms it:
"to have a snack" = перекусить or закусить/закусывать.