noun
throwaway account; burner account
Internet slang for a disposable online account used temporarily, often to avoid linking to one's main identity.
炎上しそうな意見は捨て垢で投稿した。
I posted the controversial opinion using a throwaway account.
捨て垢を作って、匿名で質問した。
I created a burner account and asked the question anonymously.
本垢 means 'main account', the opposite of a throwaway account.
From 捨てる (to throw away) + 垢 (slang abbreviation of アカウント, from English 'account'). The kanji 垢 is ateji used for its reading アカ.