Poi·son n.
 1. Any agent which, when introduced into the animal organism, is capable of producing a morbid, noxious, or deadly effect upon it; as, morphine is a deadly poison; the poison of pestilential diseases.
 2. That which taints or destroys moral purity or health; as, the poison of evil example; the poison of sin.
 Poison ash. Bot. (a) A tree of the genus Amyris (Amyris balsamifera) found in the West Indies, from the trunk of which a black liquor distills, supposed to have poisonous qualities. (b) The poison sumac (Rhus venenata). [U. S.]
 Poison dogwood Bot., poison sumac.
 Poison fang Zool., one of the superior maxillary teeth of some species of serpents, which, besides having the cavity for the pulp, is either perforated or grooved by a longitudinal canal, at the lower end of which the duct of the poison gland terminates. See Illust. under Fang.
 Poison gland Biol., a gland, in animals or plants, which secretes an acrid or venomous matter, that is conveyed along an organ capable of inflicting a wound.
 Poison hemlock Bot., a poisonous umbelliferous plant (Conium maculatum). See Hemlock.
 Poison ivy Bot., a poisonous climbing plant (formerly Rhus Toxicodendron, or Rhus radicans, now classified as Toxicodendron  radicans) of North America.  It is common as a  climbing vine, especially found on tree trunks, or walls, or as a low, spreading vine or as a shrub.  As a low vine it grows well in lightly shaded areas, recognizable by growing in clusters of three leaves.  Its leaves are trifoliate, rhombic-ovate, and variously notched.  Its form varies slightly from location to location, leading to some speculation that it may consist of more than one species.  Many people are poisoned by it, though some appear resistant to its effects.  Touching the leaves may leave a residue of an oil on the skin, and if not washed off quickly, sensitive areas of skin become reddened and develop multiple small blisters, lasting for several days to several weeks, and causing a persistent itch.  The toxic reaction is due to an oil, present in all parts of the plant except the pollen, called urushiol, the active component of which is the compound pentadecylacatechol (according to Charles">http://www.jaxmed.com/articles/Diseases/poison_ivy_dermatitis.htm">Charles H. Booras).   See Poison sumac.  It is related to poison oak, and is also called mercury.
 Poison nut. Bot. (a) Nux vomica. (b) The tree which yields this seed (Strychnos Nuxvomica). It is found on the Malabar and Coromandel coasts.
 Poison oak Bot., a dermatitis-producing plant often lumped together with the poison ivy (Toxicodendron  radicans) in common terminology, but more properly distinguished as the more shrubby  Toxicodendron  quercifolium (syn. Toxicodendron  diversilobum), common in California and Oregon.  Opinion varies as to whether the poison oak and poison ivy are only variants of a single species.  See poison ivy, above.
 Poison sac. Zool. Same as Poison gland, above. See Illust. under Fang.
 Poison sumac Bot., a poisonous shrub formerly considered to be of the genus Rhus (Rhus venenata), but now classified as Toxicodendron  vernix; -- also called poison ash, poison dogwood, and poison elder. It has pinnate leaves on graceful and slender common petioles, and usually grows in swampy places.  Both this plant and the poison ivy (Toxicodendron radicans, formerly Rhus Toxicodendron) have clusters of smooth greenish white berries, while the red-fruited species of this genus are harmless.  The tree (Rhus vernicifera) which yields the celebrated Japan lacquer is almost identical with the poison sumac, and is also very poisonous.  The juice of the poison sumac also forms a lacquer similar to that of Japan.
 Syn: -- Venom; virus; bane; pest; malignity.
 Usage: -- Poison, Venom. Poison usually denotes something received into the system by the mouth, breath, etc. Venom is something discharged from animals and received by means of a wound, as by the bite or sting of serpents, scorpions, etc. Hence, venom specifically implies some malignity of nature or purpose.
 Toxicodendron vernix
      n : smooth American swamp shrub with pinnate leaves and greenish
          flowers followed by greenish white berries; yields an
          irritating oil [syn: poison ash, poison dogwood, poison
          sumac, Rhus vernix]