interfix

Short definition from Wiktionary

Noun

1. 1
   An empty morph inserted between two morphemes in the process of word formation, such as English -i- and -o-.
2. 2
   A transfix.
3. 3
   An association link.

Verb

1. 1
   To attach or anchor (two or more parts) together.
2. 2
   To insert (an interfix) between two morphemes.