late 14c., obsolete verb replaced by conjecture (v.). Also in form congette.
Online Etymology Dictionary, © 2010 Douglas Harper
Examples from the Web for conject
Conject′urable, that may be conjectured; Conject′ural, involving conjecture: given to conjecture.
Without exaggeration, it is permissible to conject that its scope extended over twenty-five centuries.Initiation into Literature