s-word

(euphemistic) The word shit, regarded as a vulgar or taboo word.

(euphemistic) The word slut, regarded as a vulgar or taboo word.

(euphemistic, UK) The word spastic, regarded as an offensive or taboo word.

(euphemistic, US) The word spic, regarded as a vulgar or taboo word.

Any word beginning with s that is not normally taboo but is considered (often humorously) to be so in the given context; for example, socialism.