Definitions:
a substance with particular chemical properties including turning litmus red, neutralizing alkalis, and dissolving some metals; typically, a corrosive or sour-tasting liquid of this kind.

a molecule or other species which can donate a proton or accept an electron pair in reactions.

the drug lsd

containing acid or having the properties of an acid; having a ph of less than 7.

sharp-tasting or sour

(of rock, especially lava) containing a relatively high proportion of silica