bittersweet

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A woody vine of the genus Celastrus, especially the North American species C. scandens and the eastern Asian species C. orbiculata, having small, round, yellow-orange fruits that open at maturity to expose red seeds. Also called staff tree.
2. n. See bittersweet nightshade.
3. n. A dark to deep reddish orange.
4. adj. Bitter and sweet at the same time: bittersweet chocolate.
5. adj. Producing or expressing a mixture of pain and pleasure: a movie with a bittersweet ending.
6. adj. Dark to deep reddish-orange.

Century Dictionary and Cyclopedia

1. Uniting bitterness and sweetness; pleasant and painful at the same time.
2. n. That which is both bitter and sweet: as, the bitter-sweet of life.
3. n. The woody nightshade, Solanum Dulcamara, a trailing plant, native of Europe and Asia, and naturalized in the United States. Its root and branches when chewed produce first a bitter, then a sweet taste; they have long been used as a remedy in various skin-diseases. Its small scarlet berries, resembling red currants, though not absolutely poisonous, are not wholesome. The shrubby, false, or climbing bittersweet of the United States is the Celastrus scandens, also known as the staff-tree.
4. n. Same as bitter-sweeting.

Wiktionary

1. adj. Both bitter and sweet.
2. adj. Expressing contrasting emotions of pain and pleasure.
3. n. A vine, of the genus Celastrus, having small orange fruits that open to reveal red seeds.
4. n. The bittersweet nightshade, Solanum dulcamara.
5. n. A variety of apple with a bittersweet taste.

GNU Webster's 1913

1. adj. Sweet and then bitter or bitter and then sweet; esp. sweet with a bitter after taste; hence (Fig.), pleasant but painful.
2. n. Anything which is bittersweet.
3. n. A kind of apple so called.
4. n. A climbing shrub, with oval coral-red berries (Solanum dulcamara); woody nightshade. The whole plant is poisonous, and has a taste at first sweetish and then bitter. The branches are the officinal dulcamara.
5. n. An American woody climber (Celastrus scandens), whose yellow capsules open late in autumn, and disclose the red aril which covers the seeds; -- also called Roxbury waxwork.

WordNet 3.0

1. adj. tinged with sadness
2. adj. having a taste that is a mixture of bitterness and sweetness
3. n. poisonous perennial Old World vine having violet flowers and oval coral-red berries; widespread weed in North America
4. n. twining shrub of North America having yellow capsules enclosing scarlet seeds