Margaret with expression of surprise — maiden showing a lot of resistance

• Resistor unit
• Insulation tester's unit
• A unit of resistance equal to one million ohms
• Unit of electrical resistance
• A lot of resistance
• Large amount of resistance

WordNet Word definitions in WordNet
n. a unit of resistance equal to one million ohms

Wiktionary Word definitions in Wiktionary
n. (alternative spelling of megaohm English)

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Megohm \Meg"ohm"\, n. [Mega- + ohm.] (Elec.) One of the larger measures of electrical resistance, amounting to one million ohms.