Expletive

Part of speech: noun (n.)

A word, letter, or syllable not necessary to the sense, but inserted to fill a vacancy; an oath. While explectives their feeble aid to join, And ten low words oft creep in one dull line. Pope.

Part of speech: adjective (a.)

Filling up; hence, added merely for the purpose of filling up; superfluous. "Expletive imagery." Hallam. Expletive phrases to plump his speech. Barrow.