Castor Oil, a thick, smooth, yellowish liquid derived from the seeds of the castor-oil plant, or castor bean. Castor oil is used as a laxative, as a high-temperature lubricant, in the preservation of leather, and in the manufacture of paints, varnish, dyes, and soap. When it is used as a laxative, its unpleasant taste can be disguised by mixing the oil with fruit juices, or it may be taken in capsules.

In tropical regions the castor-oil plant is a tree reaching 40 feet (12 m) in height. In temperate climates it attains a height of 15 feet (4.6 m) and is grown as an annual, usually as a decorative plant in parks or gardens. It has tiny yellow flowers that grow in long clusters. The leaves are green, red, or purple. The fruit is a burlike pod containing three oval seeds, or beans. The seeds contain a substance, not found in the oil, that is highly poisonous.

The castor-oil plant is Ricinus communis of the spurge family, Euphorbiaceae.