heptode

[ hep-tohd ]
/ ˈhɛp toʊd /

noun Electronics.

a vacuum tube containing seven electrodes, usually a plate, a cathode, a control electrode, and four grids.

Origin of heptode

First recorded in 1930–35; hept- + -ode2
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019