A play on alt-right, the right-wing ultra-nationalist movement characterized by a rejection of knowledge, sanity and civility, and by the use of online media to disseminate lies, wild conspiracy theories, doxxing, and blatantly racist, sexist, monotheocratic and trans-phobic content. The "Galt" comes from John Galt - a character in Ayn Rand's Atlas Shrugged, and "Reich" comes from - well - you get the idea.
The queen of disinformation, Sarah Sanders, is giving the Galt Reich response in this years' SOTU.