资料来源 : Webster's Revised Unabridged Dictionary (1913)

Impacable \Im*pa"ca*ble\, a. [L. pref. im- not + pacare to
   quiet. See {Pacate}.]
   Not to be appeased or quieted. [Obs.] --Spenser. --
   {Im*pa"ca*bly}, adv.