šmokljan

1. colloq. derog. dork; goof; simpleton
   Ne budi šmokljan, pozovi je da izađete. — Don't be a dork, ask her out.
   U filmu glumi nekog smotanog šmokljana. — In the film he plays some clumsy goof.

Means a clumsy, dopey wimp, not a bookish person; for 'nerd, swot' Serbian uses štreber.