Present participle of bestraddle; the act of straddling over or standing astride across something.
From 'bestraddle' plus the gerund suffix '-ing.' This form expresses the ongoing or continuous action of straddling.
The '-ing' form is one of the most flexible in English—it can be a verb part, a noun, or even an adjective, which is why it's so common and useful across almost every sentence.
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