Merriam-Webster's Collegiate Dictionary, 11th Edition:
expletive --
a.: a syllable, word, or phrase inserted to fill a vacancy (as in a sentence or a metrical line) without adding to the sense; especially: a word (as it in “make it clear which you prefer”) that occupies the position of the subject or object of a verb in normal English word order and anticipates a subsequent word or phrase that supplies the needed meaningful content
b.: an exclamatory word or phrase; especially: one that is obscene or profane

Collins English Dictionary. 8th Edition:
1) an exclamation or swearword; an oath or a sound expressing an emotional reaction rather than any particular meaning
2) any syllable, word, or phrase conveying no independent meaning, esp one inserted in a line of verse for the sake of the metre

Random House Webster's Unabridged Dictionary:
1. an interjectory word or expression, frequently profane; an exclamatory oath.
2. a syllable, word, or phrase serving to fill out.
3. Gram. a word considered as regularly filling the syntactic position of another, as it in It is his duty to go, or there in There is nothing here.

Collins COBUILD Advanced Learner's English Dictionary, 5th edition:
An expletive is a rude word or expression such as ‘Damn!’ which you say when you are annoyed, excited, or in pain. (FORMAL) = swear word

Какое все это имеет отношение к "словам-паразитам"??