Remove and Disable Spotlight icon from top right bar

Hide:

sudo chmod 600 /System/Library/CoreServices/Search.bundle/Contents/MacOS/Search
killall SystemUIServer

Show it again:

sudo chmod 755 /System/Library/CoreServices/Search.bundle/Contents/MacOS/Search
killall SystemUIServer

To disable spotlight only instead, without removing it from the top menu:

sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist

To enable it again:

sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist