You can find it in many big dictionaries. Please note that the English pronunciation is different from the American pronunciation.
Post the explanations of the three dictionaries:
Oxford Advanced Learner's Dictionary
vermouth
/ ?v?m?θ; US v?r?mu?θ; v?ˋmuθ/ n (a) [U] strong white wine flavored with herbs, drunk as an aperitif (often in strong cocktails) vermouth (used as an aperitif, often mixed into cocktails). (b) [C] glass or drink of this vermouth.
American Heritage Dictionary (dual interpretation) (I don’t know why the phonetic symbols of this dictionary are garbled when pasted, so I’ll just add the etymology)
vermouth
ver.mouth
ver.mouth
vermouth
ver.mouth
p>n. (noun)
A sweet or dry wine flavored with aromatic herbs and used chiefly in mixed drinks.
Vermouth, vermouth: with aromatic herbs A sweet but non-aqueous liquor flavored by plants and used mainly in mixed drinks
Etymology:
1. French vermout
French vermout
p>
2. from German Wermut
From German Wermut
3. from Middle High German wermuot [wormwood]
From Middle High German wermuot [wormwood]
4. from Old High German wermuota
From Old High German wermuota
Longman Contemporary English Dictionary
vermouth
ver·mouth /?v?m?θ US v?r?mu?θ/ n [U]
[Date: 1800-1900; Language: French; Origin: vermout, from German wermut 'wormwood']
an alcoholic drink made from wine with herbs and spices
dry vermouth