stopping-out

from the GNU version of the Collaborative International Dictionary of English.

• noun A method adopted in etching, to keep the acid from those parts which are already sufficiently corroded, by applying varnish or other covering matter with a brush, but allowing the acid to act on the other parts.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An etching technique used to keep the acid from those parts which are already sufficiently corroded by applying varnish or other covering matter with a brush, but allowing the acid to act on the other parts.