"It's a great way to fill bars" is a reference around my apartment about games that have a "grind" element. For those don't immediately get the metaphor, it refers to games that have some kind of progress bar in it (often experience in an RPG) that one fills by various activities, and when it is filled, there is some advancement in a game. You get the idea.
How many of our games are basically bar-filling? We gain experience points to level a character, get enough science scores to give our fledgeling virtual civilization a technical advancement, or or just plain earn enouhg money to build that next railroad. A lot of our games are filling bars, meters, or coffers, often from highly repetitive behavior.