This word applies to a person that has undergone an unnecessary procedure (usually plastic surgery)due to extreme vanity / vainness
Did you hear Vera had another vainectomy? Really? Yeah, she had her eyelids done.
Doug's wife wants him to go to the plastic surgeon to have his eyes tucked. Doug has steadfastly refused his wife's pleas to undergo this vainectomy. Instead he will continue to age naturally and gracefully.