|a children's mummer's parade, as on the Fourth of July, with prizes for the best costumes.|
|a printed punctuation mark (‽), available only in some typefaces, designed to combine the question mark (?) and the exclamation point (!), indicating a mixture of query and interjection, as after a rhetorical question.|
thermionic electron tube that generates or amplifies microwaves by controlling the speed of a stream of electrons. The electrons are originally accelerated to high velocity by a potential of several hundred volts and enter a narrow gap that forms part of a cavity resonator system (see ), where they are acted upon by a radio-frequency field, which causes a bunching-up effect. Amplitude modulation of the electrons in their bunched-up state induces a strong signal as the stream passes through the gap of a second resonator. Klystrons are used in ultrahigh-frequency (UHF) circuits, such as UHF television transmission, and for microwave radar sources, where they can produce oscillations up to 400 gigahertz, in the short microwave range
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