/ ɪkˈspliːtɪv; NAmE ˈeksplətɪv/ noun
( formal ) a word, especially a rude word, that you use when you are angry, or in pain
SYN swear word
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WORD ORIGIN
late Middle English (as an adjective): from late Latin expletivus , from explere fill out, from ex- out + plere fill. The noun sense word used merely to fill out a sentence (early 17th cent.) was applied specifically to a swear word in the early 19th cent.