noun

1. an oath or exclamation, esp. an obscenity
2. a word, phrase, etc. not needed for the sense but used merely to fill out a sentence or metrical line, for grammar, rhythm, balance, etc. there in “there is nothing left” is an expletive
3. Rare anything serving as a filler

Etymology: LL expletivus, serving to fill < L expletus, pp. of explere, to fill < ex-, out, up + plere, to fill: see full

adjective