'To venture upon' definitions:

Definition of 'To venture upon'

From: GCIDE

Venture \Ven"ture\, v. i. [imp. & p. p. Ventured; p. pr. & vb. n. Venturing.]
1. To hazard one's self; to have the courage or presumption to do, undertake, or say something; to dare. --Bunyan. [1913 Webster]
2. To make a venture; to run a hazard or risk; to take the chances. [1913 Webster]
Who freights a ship to venture on the seas. --J. Dryden, Jr. [1913 Webster]
To venture at, or To venture on or To venture upon, to dare to engage in; to attempt without any certainty of success; as, it is rash to venture upon such a project. "When I venture at the comic style." --Waller. [1913 Webster]