What does a Nikon D90 dead battery look like? L?

My Nikon D90 isn't working but the battery is flashing and it looks like there's 1 bar left, I have never let my camera battery completely die there for I don't know what it looks like but my camera will turn on but none of the buttons will work and the battery icon is flashing

Go ahead and place your battery on the charger.

Yes the flashing battery icon means the battery is spent.

What does your user manual say on page 34?

Recharge it?

Eyes crossed with the tongue out.xP

Your battery is dead. Stop forcing the camera already. Recharge and if that doesn't work, buy a new battery.

Dead ones are live ones with a terminal illness caused by allowing too much electricity to go out of the terminals and not putting any back in.
You can bring them back from the dead by using current technology in the form of a terminal electricity injection interface called a charger.
Put the battery in the charger and plug the charger into the mains. Wait for a few hours for the charger to bring the battery back to life, unplug the charger and remove the battery and then put the battery into the camera.