It's a humorous Internet slang term used to refer to someone who is clumsy or tends to make mistakes repeatedly. It's a play on the name of the Pokémon 'Bulbasaur', but doesn't have any relation to it.
Examples
- Spanish: Juan es un bolbasor, siempre se olvida de las llaves de su casa.
- English: Juan is such a bolbasor, he always forgets his house keys.