noun: Initialism of seven dirty words. [Seven English-language curse words, often referred to as being the most obscene. The words, in the order George Carlin originally listed them, are: shit, piss, fuck, cunt, cocksucker, motherfucker, and tits.]
noun: (physics) Initialism of spin-density wave. [(physics) The low-energy, ground state of a metal in which densities of the electron spins and charges follow a regular spatial distribution]
