Definition of expletion in US English:

expletion

noun

  • 1The action of filling something; the state of being filled to the full, satisfaction, fulfilment.

  • 2A word, expression, or passage that merely fills out a sentence, line, or text, without adding anything to the sense; = "expletive".

  • 3An exclamation, an oath, a swear word; = "expletive". Also as a mass noun: such expletives collectively.

Origin

Early 17th century; earliest use found in Giles Fletcher. From classical Latin explētiōn-, explētiō process of perfecting, fulfilment, in post-classical Latin also completion, satisfaction, contentment from explēt-, past participial stem of explēre + -iō.