1. local specialty or souvenir bought as a gift while traveling (travelling)
じゃあお土産に買って帰ったら喜ばれるかな？Then, if I buy it as a souvenir and bring it back, would they be happy?
2. present brought by a visitor
お土産にケーキを買って、彼女の家を訪ねた。I bought a cake as a gift and went to visit her at her home.
3. something unpleasant that one is given (e.g. an illness while on vacation); unwelcome gift; disservice