Ubuntu doesn't have a built-in settings GUI to disable Unity lenses and the only way to remove a lens from Dash is to uninstall it. If you only want to temporarily disable some Unity lenses, you can use an application called Lens Toggle.
comes with a very simple user interface from which you can select to enable or disable some or all installed Unity lenses, including the default Applications, Files, Music and Video lenses
. The application may be simple, but it's very useful now that there are so many Unity lenses available
To install Lens Toggle in Ubuntu 12.04 Precise Pangolin, use the following commands:
sudo add-apt-repository ppa:aking1012-com/lenstoggle
sudo apt-get update
sudo apt-get install python-lenstoggler
Once installed, launch LensToggle from Dash.
After you've made some changes, click the Apply button in Lens Toggle and restart Unity (by typing "setsid unity" in a terminal) or log out and log back in. That's required because the application doesn't restart Unity automatically.