Involving sophisticated clandestine methods for gaining unauthorized entry and obtaining information.

To break in to a place without authorization as part of a clandestine operation. / To kidnap in order to make someone disappear (as opposed to kidnapping for ransom).

(now historical) The metal lead. / Graphite, especially as used in pencils. / (countable) A graphite pencil.

(countable, uncountable) A tree (Alnus glutinosa), of many practical uses, growing in moist conditions in Europe. / (uncountable) Wood or other product of the tree.

(historical) A former principality in Eastern Europe.

(simile) Completely black.

Cygnus atratus, an Australian swan whose feathers are black. / (figuratively) Something believed impossible or not to exist, of which an example is subsequently found.

A tree of the species Betula lenta, with a dark bark resembling a cherry tree's and an aromatic bark and sap used for birch beer.

A tinamou, Tinamus osgoodi.

rain contaminated by fungi spores, soot, or other particulate matter / radioactive rain that fell on Hiroshima following the atomic bombing of 1945