A tentative proposal, hint, or question put forward in order to ascertain another's opinions or intentions, or to elicit information. Frequently in to…

A project or piece of policy put forward to test the feeling or attitude of a person or body of people; an experimental measure or proposal, a…

to fly (or send up) a kite (figurative): to try ‘how the wind blows’, i.e. in what direction affairs are tending. (See also 4) A proposal or…

= ballon d'essai, n.