carbamic acid

from The American Heritage® Dictionary of the English Language, 4th Edition

• n. A hypothetical acid, NH2COOH, that exists only in the form of its esters and salts.

from Wiktionary, Creative Commons Attribution/Share-Alike License

• n. amino-formic acid, NH2COOH; it is too unstable to have been isolated, but its esters and salts are known.

from the GNU version of the Collaborative International Dictionary of English

• adj. an amido acid, H2N.CO2.H, not existing in the free state, but occurring as a salt of ammonium in commercial ammonium carbonate; -- called also amido formic acid.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• n. an acid that is known only by virtue of its salts (as ammonium carbamate) or its esters (as urethane)