To teeter means to rock or sway unsteadily, as if you might fall over at any moment. Picture yourself walking across a narrow log over a stream: you wobble back and forth, arms spread wide, teetering as you fight to keep your balance. Or imagine stacking blocks so high that the tower starts to lean and shake, teetering dangerously before it crashes down.

The word captures that wobbly, uncertain movement when something is barely balanced. A bicycle teeters when you're learning to ride, wobbling left and right before you get the hang of it. A person carrying a tall stack of books might teeter down the hallway, swaying with each step.

You can also use teeter to describe being caught between two choices or situations. A student who hasn't been doing their work all semester might be teetering on the edge of failing, or a team tied late in the game is teetering between victory and defeat. The phrase “teetering on the brink” means being right at the edge of something significant, usually something unwelcome.

The word is related to teeter-totter, another name for a seesaw, which tips back and forth as children ride it. That same back-and-forth motion is what it means to teeter.