antacid

n. acid neutralizer, substance which counteracts acidity

adj. counteracting acidity (mainly in the stomach)

An antacid is any substance, generally a base, which counteracts stomach acidity. In other words, antacids are stomach acid neutralizers.
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Antacid /ant·ac·id/ counteracting acidity; an agent that so acts. ant·ac·id or an·ti·ac·id adj. Counteracting or neutralizing acidity, especially of [more]Antacid - Community and Resources

Noun
1. an agent that counteracts or neutralizes acidity (especially in the stomach)
(synonym) gastric antacid, alkalizer, alkaliser, antiacid
(hypernym) agent
(hyponym) cimetidine, Tagamet
Adjective
1. acting to neutralize acid (especially in the stomach)
(similar) counteractive, antagonistic

n. antacid, acid neutralizer, substance which counteracts acidity