majority leader - the leader of the majority party in either the House or the Senate.

Malthusian - based on the theories of British economist Thomas Robert Malthus (1766-1834), who argued that population tends to increase faster than food supply, with inevitably disastrous results, unless the increase in population is checked by moral restraints or by war, famine, and disease.

mammal - an animal that feeds its young with milk secreted from mammary glands and has hair on its skin.

managed growth - growth or expansion that is controlled so as not to be harmful.

manatee - a plant-eating aquatic mammal found in the waters of Florida, the Caribbean, and off the coast of West Africa.

marbled murrelet - a rare and imperiled bird that nests in ancient forests on the west coast of the U.S.

marine mammal - a mammal that lives in the ocean, such as a whale.

mark-up - action by a Congressional committee to amend and/or approve a bill; following mark-up the bill is "reported" out of committee and is ready for consideration by the entire House or Senate.

marsh - wetland, swamp, or bog.

mass transit - see public transportation.

medfly - the Mediterranean fruit fly, a flying insect.

megalopolis - a large city expanding so fast that city government cannot adjust to provide services (such as garbage disposal).

methyl bromide - the gaseous compound CH3Br used primarily as an insect fumigant; found to be harmful to the stratospheric ozone layer which protects life on earth from excessive ultraviolet radiation.

mining - the removal of minerals (like coal , gold, or silver) from the ground.

minority leader - the leader of the minority party in either the House or the Senate.

Minuteman - an American-made ICBM; 500 Minuteman III ICBMs are deployed currently in the United States.

moratorium - legislative action which prevents a federal agency from taking a specific action or implementing a specific law.

mulch - leaves, straw or compost used to cover growing plants to protect them from the wind or cold.