| 22nd Amendment |
an amendment to the U.S. Constitution that ensures that no person can be elected to more than two four-year terms as President of the United States. The 22nd Amendment, ratified in 1951, was passed in reaction to President Franklin D. Roosevelt's four terms in office. |
| acid |
in chemistry, any of a group of substances that usu. dissolve in water, have a sour taste, and form salts in reaction with bases. (Cf. base.) [1/7 definitions] |
| allergen |
any substance capable of causing an allergic reaction. |
| allergenic |
capable of causing an allergic reaction. |
| allergic |
having abnormal or disabling sensitivity to certain agents such as drugs, food, or pollen, resulting in a hypersensitive reaction upon exposure (usu. fol. by "to"). [1/3 definitions] |
| anaphylaxis |
extreme allergic reaction to a substance, typically a foreign protein or drug, following a previous exposure to the same substance. |
| backlash |
a strong reaction against some prior development, esp. political or social change. [1/3 definitions] |
| blocker |
a drug or other substance that inhibits or prevents a biochemical reaction in an organism. [1/2 definitions] |
| break into |
to suddenly begin to display (evidence of an emotional or physical reaction). [1/6 definitions] |
| carry away |
to cause an extreme reaction; transport; enrapture. |
| catalysis |
the introduction or intervention of a substance that causes or speeds up a chemical reaction without being affected itself. [1/2 definitions] |
| catalyst |
a substance that produces or speeds up a chemical reaction without being affected itself. [1/2 definitions] |
| chain-react |
to be part of or involved in a chain reaction. |
| chain reaction |
in physics, a self-sustaining reaction in which the particles produced by nuclear fission cause the fission of other nuclei. [2/3 definitions] |
| chemical |
a distinct substance, such as an element or molecular compound, used in or obtained through a reaction involving atomic or molecular changes. [1/3 definitions] |
| chemosynthesis |
the synthesis of organic substances by an organism using energy provided by a chemical reaction. |
| control rod |
a rod or bar in a nuclear reactor that contains a neutron-absorbing material, and that is lowered into or raised from the core to control the fission chain reaction. |
| counterreaction |
combined form of reaction. |
| creep |
(informal, pl.) a feeling of uneasiness or loathing as if in reaction to something fearful crawling over one's skin (prec. by "the"). [1/12 definitions] |
| critical |
in physics, of a state just preceding a nuclear reaction. [1/6 definitions] |
| critical mass |
the minimum mass of fissionable material necessary to sustain a nuclear chain reaction. [1/2 definitions] |