From Longman Dictionary of Contemporary Englishcover yourself (against something)cover yourself (against something) (also cover your back, cover your butt/ass American English) to do things in a way that will prevent people from blaming or criticizing you Doctors are concerned to cover themselves against charges of negligence. He copied Stella in on the email just to cover his back. → cover
Examples from the Corpus
cover yourself (against something)• In a sense it was inevitable that Kelly should cover himself in glory.• He covers himself in rose-water all the time so that the place smells like a funeral parlour.• Dealers will no longer need to buy to cover themselves, removing one factor that has supported prices.• My landlady had stopped screaming by now because she'd managed to cover herself up.• He covered himself with a blanket that suddenly seemed to move on its own-an army of insects began crawling over his skin.• I slid out of bed and covered myself with a huge paisley shawl.• He tumbled to the ground, writhed around on the dirt and covered himself with dust.• She told him that he would cover himself with ridicule by bringing the boy back. 