The chemical compound in hot peppers that creates the burning sensation when you eat them.
From Spanish 'capsicum' (pepper plant) + '-in' suffix for chemical compounds; the term was coined in the 1800s when chemists isolated the active ingredient.
Capsaicin tricks your brain into thinking your mouth is on fire—it actually binds to pain receptors, which is why it's now used in topical creams to relieve arthritis and neuropathic pain!
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