"device giving a signal about some physical activity," 1947, from a shortened form of sensory (q.v.) or an agent noun in Latin form from sense (v.).

"instrument for measuring the forces of gravity," 1797, from French gravimètre, from gravité (see gravity) + -mètre "measuring device" (see -meter).

"device for connecting computers and electronic musical instruments," 1983, acronym for Musical Instrument Digital Interface.

"machine for separating cotton from seeds," 1796, American English, used earlier of other machineries, especially of war or torture, from Middle English gin "ingenious device, contrivance" (c. 1200), from Old French gin "machine, device, scheme," shortened form of engin (see engine). The verb in this sense is recorded from 1789. Related: Ginned; ginning. Middle English had ginful "ingenious, crafty; guileful, treacherous" (c. 1300).

also fly-wheel, "heavy-rimmed revolving wheel to regulate motion," 1784, from fly (n.) "speed-regulating device" (1590s, from fly (v.1)) + wheel (n.).

also switch-board, "device for making interchangeable connections between many circuits," 1867, from switch (n.) + board (n.1).

1838, in hydraulics, "device for filtering impurities from water," from sand (n.) + trap (n.). As "golf bunker," by 1906.

1650s, "one who regulates" in any sense, agent noun in Latin form from regulate. In English history from 1680s; in American history from 1767, applied to local posses that kept order (or disturbed it) in rural regions. From 1702 as "device for controlling machinery in motion;" the specific sense of "mechanical device or clock used to set the time of other pieces" is from 1758.

also on-line, in reference to computers, "directly connected to a peripheral device," 1950; see on + line (n.).

"device to listen in secretly on telephone calls," 1923, from tap (v.2) in the "listen secretly" sense.