ac·id (ăsˈĭd)

1. Any of a large class of sour-tasting substances whose aqueous solutions are capable of turning blue litmus indicators red, of reacting with and dissolving certain metals to form salts, and of reacting with bases or alkalis to form salts.
2. A substance that ionizes in solution to give the positive ion of the solvent.
3. A substance capable of yielding hydrogen ions.
4. A proton donor.
5. An electron acceptor.
6. A molecule or ion that can combine with another by forming a covalent bond with two electrons of the other.
7. A substance having a sour taste.
8. See LSD.

1. Of or relating to an acid.
2. Having a high concentration of acid.
3. Having a sour taste.