The American Heritage® Dictionary of the English Language, 4th Edition
n. A bitter poisonous alkaloid, C45H73NO15, derived from potato sprouts, tomatoes, and nightshade and having narcotic properties formerly used to treat epilepsy.
n. A poisonous glycoalkaloid found in many species of the nightshade family.
the GNU version of the Collaborative International Dictionary of English
n. A poisonous alkaloid glucoside extracted from the berries of common nightshade (Solanum nigrum), and of bittersweet, and from potato sprouts, as a white crystalline substance having an acrid, burning taste; -- called also solonia, and solanina.
The Century Dictionary and Cyclopedia
n. A complex body, either itself an alkaloid or containing an alkaloid, the active principle of bittersweet, Solanum Dulcamara. It is a narcotic poison.
Word Usage
"Unripe tomatoes and the green "eyes" of potatoes contain solanine which can cause moderate nausea, vomiting, headache and diarrhea."