sensitive plant

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A shrubby tropical American plant (Mimosa pudica) having mauve flower heads and bipinnately compound leaves with leaflets and leafstalks that fold and droop when touched. Also called touch-me-not.
2. n. Any of various similar plants, such as Cassia nictitans, of eastern and central North America.

Century Dictionary and Cyclopedia

1. n. The tropical and greenhouse plant Mimosa pudica; the humble-plant. It is mechanically irritable in a higher degree than almost any other plant. The leaves are bipinnate, the very numerous linear leaflets ranked on two pairs of branches which are inserted close to the end of the common petiole, thus appearing digitate. At night each leaf curves downward and the leaflets fold together, and in the daytime a slight touch causes them to assume the same position. It has purple flowers in heads on long peduncles. It is widely diffused through the tropics, native at least in South America and naturalized in the southern United States. The name is extended to other sensitive mimosas, as M. sensitive, which is irritable in a less degree, and sometimes to the whole genus.
2. n. Same as sensitive pea (which see, under pea).
3. n. The narrow-leaved sensitive-brier, Leptoglottis angustata (Schrankia angustata of Torrey and Gray), found from Virginia to Florida aud west to Tennessee and Texas.

GNU Webster's 1913

1. adj. (Bot.) Any plant showing motions after irritation, as the sensitive brier (Schrankia) of the Southern States, two common American species of Cassia (C. nictitans, and C. Chamæcrista), a kind of sorrel (Oxalis sensitiva), etc.

WordNet 3.0

1. n. semi-climbing prickly evergreen shrub of tropical America having compound leaves sensitive to light and touch
2. n. prostrate or semi-erect subshrub of tropical America, and Australia; heavily armed with recurved thorns and having sensitive soft grey-green leaflets that fold and droop at night or when touched or cooled