Noun

1. An empty morph inserted between two morphemes in the process of word formation.
   • 2004, Francis Katamba, Morphology: Critical Concepts in Linguistics http://books.google.com/books?id=QBsKpjIh3J8C, ISBN 0415270790, page 187:

   An empty morph is an interfix if it fulfills all of the following three conditions (Dressier, 1985f).

2. An association link, a device to group multiple words or concepts.
   • 1959, Frank S. Wagner, Jr., A Dictionary of Documentation Terms http://books.google.com/books?id=MlgZAAAAMAAJ, page 19:

   LOCANT, n. A number used in the Dyson cipher system for coding the position of substituents of carbon chain, i.e. an interfix.

Verb

1. To attach or anchor two or more parts together.
   • 1932, Elmer G. Koch, "Collar Fastener", United States Patent 1915250 http://www.google.com/patents?id=tpZPAAAAEBAJ, page 2:

   Generally speaking the article is formed of two pieces which are interfixed for providing a pair of spring urged jaws...

2. To insert an interfix between two morphemes.
   • 2001, Wolfgang U. Dressler et al., "The Processing of interfixed German compounds", in Yearbook of Morphology 1999 http://books.google.com/books?id=igymN2VyWB8C, ISBN 079236631X, page 185:

   Our goal in the construction of this task was to isolate and highlight the relationship between the interfixed and free forms of the initial constituent.