Nouns

(n)bittersweet, bittersweet nightshade, climbing nightshade, deadly nightshade, poisonous nightshade, woody nightshade, Solanum dulcamarapoisonous perennial Old World vine having violet flowers and oval coral-red berries; widespread weed in North America
(n)bittersweet, American bittersweet, climbing bittersweet, false bittersweet, staff vine, waxwork, shrubby bittersweet, Celastrus scandenstwining shrub of North America having yellow capsules enclosing scarlet seeds

Adjectives

(s)bittersweettinged with sadness“a movie with a bittersweet ending”
(s)bittersweet, semisweethaving a taste that is a mixture of bitterness and sweetness