1.  horehound(n = noun.plant) - any of various aromatic herbs of the genus Marrubium;
is a kind of herb, herbaceous plant
is a member of genus marrubium, marrubium
has particulars: common horehound, marrubium vulgare, white horehound

2.  horehound(n = noun.food) - a candy that is flavored with an extract of the horehound plant;
is a kind of candy, confect

1.  A plant of the genus Marrubium (Marrubium vulgare), which has a bitter taste, and is a weak tonic, used as a household remedy for colds, coughing, etc. [1913 Webster]

2.  A lozenge or tablet, usually sweetened, containing extract of horehound, used as a remedy for a cough or a sore throat. [PJC]

horehound, n. (also hoarhound)
1 a a herbaceous plant, Marrubium vulgare, with a white cottony covering on its stem and leaves. b its bitter aromatic juice used against coughs etc.
2 a herbaceous plant, Ballota nigra, with an unpleasant aroma.

Etymology:
OE hare hune f. har HOAR + hune a plant

N  fragrance, aroma, redolence, perfume, bouquet, essence, scent, sweet smell, aromatic perfume, agalloch, agallochium, aloes wood, bay rum, calambac, calambour, champak, horehound, lign-aloes, marrubium, mint, muskrat, napha water, olibanum, spirit of myrcia, essential oil, incense, musk, frankincense, pastil, pastille, myrrh, perfumes of Arabia, otto, ottar, attar, bergamot, balm, civet, potpourri, pulvil, nosegay, scentbag, sachet, smelling bottle, vinaigrette, eau de Cologne, toilet water, lotion, after-shave lotion, thurification, perfumer, eucalyptus oil, pinene, fragrant, aromatic, redolent, spicy, savory, balmy, scented, sweet-smelling, sweet-scented, perfumed, perfumatory, thuriferous, fragrant as a rose, muscadine, ambrosial.

black horehound, common horehound, fetid horehound, stinking horehound, water horehound, white horehound