Castor oil \Cas"tor oil\ (k[a^]s"t[~e]r oil`). A mild cathartic oil, expressed or extracted from the seeds of the Ricinus communis, or Palma Christi. When fresh the oil is inodorous and insipid.

Castor-oil plant. Same as Palma Christi.

Source: Webster's Revised Unabridged Dictionary (1913)