터미널을 켜서 아래 커맨드 실행

defaults write com.apple.dock autohide -bool true && defaults write com.apple.dock autohide-delay -float 0 && defaults write com.apple.dock autohide-time-modifier -float 0 && killall Dock

원상복귀

defaults delete com.apple.dock autohide && defaults delete com.apple.dock autohide-delay && defaults delete com.apple.dock autohide-time-modifier && killall Dock