bittersweet

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Bitter and sweet at the same time.
• adjective Producing or expressing a mixture of pain and pleasure.
• adjective Dark to deep reddish-orange.
• noun Any of various woody vines of the genus Celastrus, especially C. scandens, native to North America, and C. orbiculata, an eastern Asian species that is widespread in North America, having small, round, yellow-orange fruits that open at maturity to expose red seeds.
• noun A dark to deep reddish orange.

from The Century Dictionary.

• Uniting bitterness and sweetness; pleasant and painful at the same time.
• noun That which is both bitter and sweet: as, the bitter-sweet of life.
• noun The woody nightshade, Solanum Dulcamara, a trailing plant, native of Europe and Asia, and naturalized in the United States.
• noun Same as bitter-sweeting.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Sweet and then bitter or bitter and then sweet; esp. sweet with a bitter after taste; hence (Fig.), pleasant but painful.
• noun Anything which is bittersweet.
• noun A kind of apple so called.
• noun 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.
• noun 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective Both bitter and sweet.
• adjective Expressing contrasting emotions of pain and pleasure.
• noun A vine, of the genus Celastrus, having small orange fruits that open to reveal red seeds.
• noun The bittersweet nightshade, Solanum dulcamara.
• noun A variety of apple with a bittersweet taste.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective tinged with sadness
• adjective having a taste that is a mixture of bitterness and sweetness
• noun poisonous perennial Old World vine having violet flowers and oval coral-red berries; widespread weed in North America
• noun twining shrub of North America having yellow capsules enclosing scarlet seeds