any of a group of nitrogenous basic compounds found in plants, typically insoluble in water and physiologically active. Common examples are morphine, strychnine, quinine, nicotine, and caffeine
WordReference Random House Learner's Dictionary of American English © 2025
al•ka•loid /ˈælkəˌlɔɪd/USA pronunciation n. [countable]
adj.
WordReference Random House Unabridged Dictionary of American English © 2025- Biochemistrya bitter-tasting chemical compound common in plants, as caffeine, morphine, and nicotine.
adj.
- Biochemistry, Chemistry, Drugsresembling an alkali;
alkaline.
al•ka•loid
(al′kə loid′),USA pronunciation [Biochem., Chem.,]Pharm.
n.
adj.
n.
- Biochemistry, Chemistry, Drugsany of a large class of organic, nitrogen-containing ring compounds of vegetable origin and sometimes synthesized, some of which are liquid but most of which are solid, that have a bitter taste, that are usually water-insoluble and alcohol-soluble, that combine with acids without the loss of a water molecule to form water-soluble hydrochlorides, hydrobromides, or the like, and that usually exhibit pharmacological action, as nicotine, morphine, or quinine.
adj.
- Biochemistry, Chemistry, Drugsresembling an alkali;
alkaline.
- alkal(i) + -oid 1825–35
Collins Concise English Dictionary © HarperCollins Publishers::
'alkaloid' also found in these entries (note: many are not synonyms or translations):
-oid
- alkaloidal
- anatabine
- apomorphine
- arecoline
- atropine
- ayahuasca
- bebeerine
- belladonna
- berberine
- betaine
- bromocriptine
- brucine
- caffeine
- cinchonidine
- cinchonine
- cocaine
- codeine
- colchicine
- coniine
- delphinine
- deserpidine
- dihydroergotamine
- ephedrine
- ergonovine
- ergotoxine
- essence
- greenheart
- hydrastine
- hydrastinine
- hydrobromide
- hydrochloride
- hydrosulfate
- hyoscyamine
- ibogaine
- jaborandi
- lobeline
- methysergide
- morphine
- narceine
- nicotine
- nornicotine
- papaverine
- pereirine
- physostigmine
- pilocarpine
- piperidine
- piperine
- quinacrine
- quinidine