1. Literally, an arcade game in which the player uses a small rubber mallet to hit robotic toy moles that pop up randomly in holes laid out across the surface of the machine. I love coming to this old arcade. I have a lot of fond memories playing whack-a-mole and skee ball here as a kid.

2. By extension, a situation in which problems continue to arise faster than one is able to solve or cope with them, resulting in piecemeal, incomplete, or temporary results. These dang pop-up ads are so annoying! It's a game of whack-a-mole every time I go online these days! Every time we think we have the software debugged, more problems show up. We've just been playing whack-a-mole from day one!