Meaning of split infinitive

split' infin'itive

Pronunciation: [key]
— Gram. Gram.
  1. an expression in which there is a word or phrase, esp. an adverb or adverbial phrase, between to and its accompanying verb form in an infinitive, as in to readily understand.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.