ohm

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A unit of electrical resistance equal to that of a conductor in which a current of one ampere is produced by a potential of one volt across its terminals. See Table at measurement.

Century Dictionary and Cyclopedia

1. n. In electricity, the unit of resistance (see resistance). The theoretical or absolute ohm is equal to 10 centimeter-gram-second units of resistance (see unit). The practical ohm, until recently in use, was a resistance equal to that of a certain standard coil of wire (German silver) constructed under the direction of a Committee of the British Association in 1863, and hence often called the B. A. unit of resistance; it is a little less (0.987) than the true ohm. The legal or congress ohm, adopted by the Electrical Congress in 1884, is defined as the resistance at 0° C. of a column of pure mercury which is one square millimeter in cross-section and 106 centimeters in length; it is a very little less than the theoretical ohm. The Siemens unit is somewhat less than the ohm, being the resistance of a similar column just one meter in length. The resistance of a copper wire 1,000 feet long and one tenth of an inch in diameter is very nearly one ohm; a mile of ordinary iron telegraph-wire has a resistance of nearly 13 ohms.
2. n. An abbreviation of On His (or Her) Majesty's Service.

Wiktionary

1. n. In the International System of Units, the derived unit of electrical resistance; the electrical resistance of a device across which a potential difference of one volt causes a current of one ampere. Symbol: Ω

GNU Webster's 1913

1. n. (Elec.) The standard unit in the measure of electrical resistance, being the resistance of a circuit in which a potential difference of one volt produces a current of one ampére. As defined by the International Electrical Congress in 1893, and by United States Statute, it is a resistance substantially equal to 109 units of resistance of the C. G. S. system of electro-magnetic units, and is represented by the resistance offered to an unvarying electric current by a column of mercury at the temperature of melting ice 14.4521 grams in mass, of a constant cross-sectional area, and of the length of 106.3 centimeters. As thus defined it is called the international ohm.

WordNet 3.0

1. n. a unit of electrical resistance equal to the resistance between two points on a conductor when a potential difference of one volt between them produces a current of one ampere
2. n. German physicist who formulated Ohm's law (1787-1854)