情けない is an adjective meaning pathetic, miserable, or shameful. Originally meaning heartless, its modern usage describes a feeling of disappointment or shame toward someone acting weak or failing to meet expectations.
That is how Fuguro works. It brings 情けない back for review right before you forget it, each time a little later, until it sticks for good. You hear it spoken aloud, and you meet it again in stories you can already read. The first five levels are free.