Wordnet 3.0
VERB (1)
1. 
 act together or towards others or with others; 
- Example: "He should interact more with his colleagues"
The Collaborative International Dictionary of English v.0.48:
Interact \In`ter*act"\, n. [Pref. inter- + act. Cf.
   Entr'acte.]
   A short act or piece between others, as in a play; an
   interlude; hence, intermediate employment or time.
   --Chesterfield.
   [1913 Webster]
The Collaborative International Dictionary of English v.0.48:
Interact \In`ter*act"\, v. i.
   To act upon each other; as, two agents mutually interact.
   --Emerson. --Tyndall.
   [1913 Webster]
WordNet (r) 3.0 (2006):
interact
    v 1: act together or towards others or with others; "He should
         interact more with his colleagues"