I'd say it was a simile, as an explicit comparison is made between two essentially dissimilar things. Personally, I don't think it works well. I'm not totally sure what it means as, to me, 'tapers' is ambiguous.
Subjectivity and taste plays a huge part. Creating good, original figures of speech is an art. A lot depends on whether the writer is trying to provoke laughter, a wry smile, emotional empathy, and so on.
'My love is like a red, red rose' or
'My love is like a waterlogged boot'
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