(chemistry) A transitional structure, in an energetically excited state, that forms between the reactants of a chemical reaction and breaks down to form the products

The specific compound in a natural or man-made mixture that is responsible for the mixture's activity.

(astronomy) A galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy.

(chemistry, of a crystal or compound) Exhibiting optical activity.

(physics) a property caused by asymmetrical molecular or crystal structure that enables a compound or crystal to rotate the plane of incident polarized light

capable of lowering the surface tension of a liquid

Any activity done by an astronaut outside of a spacecraft etc; a spacewalk or moonwalk.

(law, often derogatory) The act of replacing an impartial interpretation of existing law with the judge's personal feelings about what the law should be.

(physics, meteorology) The boundary between two different air masses, or a portion thereof, which produces appreciable cloudiness and precipitation and is usually accompanied by significant shifts in wind direction.

Sewage that has been aerated and agitated in order to promote the growth of beneficial microorganisms that break down organic matter.