The Dock may be one of the handiest features introduced in OS X and the newer macOS. By default, the Dock is located across the bottom of the screen, and is always in view.
No matter how wrong that view might be, Apple designed the Dock to be flexible. You can easily change the Dock’s settings, so it only appears when you move the cursor over it. Unfortunately, the Dock’s autohide feature comes bundled with an animation that results in a perceivable delay. You may use a simple terminal command to alter the autohide delay for the Dock.
First, enable autohide behavior for the Dock
To enable Dock autohide, right click on the Dock separator and select Turn Hiding On. You can also do so via System Preferences → Dock, or simply use the Option (⌥)+Command (⌘)+D keyboard shortcut for quick hiding and revealing.
Next, remove the Dock autohide animation
To open Terminal, go to Finder and navigate to Applications → Utilities. Once Terminal is open, simply paste the following command into the Terminal window and press Return on the keyboard:
defaults write com.apple.dock autohide-time-modifier -int 0;killall Dock
This command sets the Dock autohide time to 0, effectively removing the animation. It also restarts the Dock so that the changes to the autohide time take effect as soon as the command is used.
How to restore the autohide animation
Restoring the stock autohide animation for the Dock is easy. The following Terminal command will delete the values associated with the autohide time modifier, restoring the default animation.
defaults delete com.apple.dock autohide-time-modifier;killall Dock