expletive

adj

1. Serving to fill up, merely for effect, otherwise redundant.

   “No one entered more fully than Shakespeare into the character of this species of poetry, which admits of no expletive imagery, no merely ornamental line.”

   “deprecating being taken for ſerious, or to be underſtood that he meaneth any thing by them; but only that he uſeth them as expletive phraſes ... to plump his ſpeech, and fill up ſentences.”

2. Marked by expletives (phrase-fillers).

noun

1. A profane, vulgar term, notably a curse or obscene oath.

   “If we don't take advantage of any [expletive] in any way, then it's our loss.”

2. A word without meaning added to fill a syntactic position.
3. A word that adds to the strength of a phrase without affecting its meaning (such as fuckin in "there's no fuckin way he's gonna get away with it").
4. An obscene or otherwise offensive interjection (such as shit, fuck, or damn it).