meta-acid
/ˈmɛtəˌasɪd/Chemistry. Now rare
noun
1The least hydrated of a series of oxoacids formed from the same anhydride.
2Now usually with meta italicized. The meta isomer of a disubstituted aromatic acid.
Origin
Mid 19th century; earliest use found in Thomas Graham (1805–1869), chemist. From meta- + acid.