"pertaining to the system of weights and measures based on the meter," 1855, from French métrique, from mèter (see meter (n.2)). In this sense, metrical is attested from 1797. Metric system is attested by 1855.

Paris underground, 1904, from French abbreviation of Chemin de Fer Métropolitain "Metropolitan Railway" (see metropolitan (adj.)). French chemin de fer "railroad" is literally "iron road." Construction began in 1898.

"beyond the sphere of logic, transcending logic," by 1865; see meta- in the third sense of "transcending, overarching, dealing with the most fundamental matters of" + logical. Related: Metalogic (n.), by 1842; metalogical.

"treatment of disease by the external application of metals," by 1856, from metallon, Greek source of metal (n.) + therapy.

First formulated as a system by Burq in 1848, and hence often called Burqism, it has been recently revived by Charcot. Simple disks of various metals are employed in contact with the external parts of the body, from which different therapeutic results are claimed. Other observers assert that all the phenomena described as following the application of metals may be produced by disks of wood, and that whatever curative results are attained are due to mental effects, rather than to any special virtues emanating from the metals themselves. [Century Dictionary, 1895]

"the science of smelting," 1670s, from Modern Latin metallurgia, from Greek metallourgos "worker in metal," from metallon "metal" (see metal) + -ergos "that works," from ergon "work" (from PIE root *werg- "to do"). Related: Metallurgical; metallurgist (1660s).

"to undergo metathesis," 1893, from metathesis + -ize. Related: Metathesized; metathesizing.

"metropolitan spirit, ideas, or institutions," 1855, from metropolitan (adj.) + -ism.

"full of spirit, fiery, courageous," 1660s, from mettle + -some (1). Related: Mettlesomely; mettlesomeness.