What is a figure having a polygon base and triangular sides which meet in a point at the top?

well, it could be almost anything because a ploygon is a closed shape that has three or more lines. But the most main answer would be a triangular pyramid.

well, it could be almost anything because a ploygon is a closed shape that has three or more lines. But the most main answer would be a triangular pyramid.

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It could not be almost anything. It IS a pyramid, which consists of a polygonal base with triangular sides meeting at an apex or a point at the top. That is what a pyramid is.