bittersweet

(noun) poisonous perennial Old World vine having violet flowers and oval coral-red berries; widespread weed in North America. Synonyms: bittersweet nightshade, climbing nightshade, deadly nightshade, poisonous nightshade, woody nightshade, Solanum dulcamara.

(noun) twining shrub of North America having yellow capsules enclosing scarlet seeds. Synonyms: American bittersweet, climbing bittersweet, false bittersweet, staff vine, waxwork, shrubby bittersweet, Celastrus scandens.

(adj) tinged with sadness. Example: "A movie with a bittersweet ending."

(adj) having a taste that is a mixture of bitterness and sweetness. Synonyms: semisweet.