The present participle of circuit, meaning to connect in a circuit or to travel in a circular route.
From the verb circuit with the gerund/present participle suffix -ing. Circuit as a verb emerged from the noun, following the pattern where English nouns frequently become verbs.
English is wonderfully flexible: a noun becomes a verb through sheer use. Once people said 'I'm making a circuit,' they shortened it to 'I'm circuiting,' and the verb was born. Most English words are shape-shifters.
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