This word is a portmanteau (or say blend for simplicity) of Flow and Vocabulary. Flocabulary is the concept which emphasizes on getting augmentation of vocabulary by using flow of rap music. The idea originated (as per the founder of the institution) when he was preparing for SAT examinations and wanted to make tedious process of vocabulary improvement easier and more fun.
As you can see in this hilarious but substantial video on William Shakespeare’s ‘Much Ado about Nothing’ http://flocabulary.com/muchado/; Flocabulary indeed makes it fun to learn. They call it ‘Hip-Hop in classrooms’. There have been studies suggesting efficacies of these Flocabulary programs but my acquaintance with this concept and the course is very new and hence restrains me from making any viable comment about their significance. One thing which my experience tells me is: It is incontrovertible that games are most effective ways of learning. It might be linguistic or any other form of learning. Games bring an unimpeachable state of flow which traditional draconian drill patterns of education can never reinforce.