The Collaborative International Dictionary of English v.0.48:

Actionary \Ac"tion*a*ry\, Actionist \Ac"tion*ist\, n. [Cf. F.
   actionnaire.] (Com.)
   A shareholder in joint-stock company. [Obs.]
   [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

ACTIONARY. A commercial term used among foreigners, to signify stockholders.