The Collaborative International Dictionary of English v.0.48:

Coadventure \Co`ad*ven"ture\, v. i.
   To share in a venture. --Howell.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Coadventure \Co`ad*ven"ture\ (?; 135), n.
   An adventure in which two or more persons are partakers.
   [1913 Webster]