Acid a. : Sour, sharp, or biting to the taste; tart; having the taste of vinegar: as, acid fruits or liquors. Also fig.: Sour-tempered.

Acid a. : Of or pertaining to an acid; as, acid reaction.

Acid n. : A sour substance.

Acid n. : One of a class of compounds, generally but not always distinguished by their sour taste, solubility in water, and reddening of vegetable blue or violet colors. They are also characterized by the power of destroying the distinctive properties of alkalies or bases, combining with them to form salts, at the same time losing their own peculiar properties. They all contain hydrogen, united with a more negative element or radical, either alone, or more generally with oxygen, and take their names from this negative element or radical. Those which contain no oxygen are sometimes called hydracids in distinction from the others which are called oxygen acids or oxacids.

Example:
When titrating Acids and bases, why do you rinse the pipette with Acid solution before titration?

Taxonomy
acids, proton, aq, bond, reactions, H2O, H3O, HCl, hydrogen, molecule, electrons, atom, conjugate base, Lewis acids, oxygen, Ka, electronegative, Ka1.

Defination from the web:
acids in chemistry. For the drug, see Lysergic acid diethylamide. For other uses, see Acid (disambiguation). "Acidity" redirects here. ... Arrhenius acids. 1.2 Brønsted acids. 1.3 Lewis acids. 2 Dissociation and equilibrium. 3 Nomenclature. 4 Acid strength. 4.1 ...