'Split infinitive' definitions:

Definition of 'split infinitive'

From: WordNet
noun
An infinitive with an adverb between `to' and the verb (e.g., `to boldly go')

Definition of 'Split infinitive'

From: GCIDE
  • Split infinitive \Split infinitive\ (Gram.) A simple infinitive with to, having a modifier between the verb and the to; as in, to largely decrease. Called also cleft infinitive.
  • Note: The use of the split infinitive is commonly considered to be ungrammatical, but by most grammarians it is considered acceptible. [Webster 1913 Suppl. +PJC]