The Collaborative International Dictionary of English v.0.48:

Indocible \In*doc"i*ble\, a. [L. indocibilis. See In- not, and
   Docible.]
   Incapable of being taught, or not easily instructed; dull in
   intellect; intractable; unteachable; indocile. --Bp. Hall. --
   In*doc"i*ble*ness, n.
   [1913 Webster]