I'm arguing with a guy about this. He says the T at the end is sibilant, and he pronounces it as "violets"
I don't know English grammar well enough to be certain, but from my Googling, it doesn't seem to be the case that a singular T can be sibilant. It would have to be "th," like in "this." And it also doesn't sound correct to me anyway.
So to answer the question you were actually asking (instead of getting into unrelated literary terms which clearly have nothing to do with pronunciation):
No, the "t" in "violet" is not generally pronounced with any sibilance. In fact, I don't believe I've ever heard anyone pronounce it that way in my life. It is pronounced in the usual way, similarly to the "t" in "pet" or "hot".
I am actually a little curious where that person is from, now.. It is possible this is a regional accent, but if so I suspect it's a pretty small region...
"Sibilance" is a rather strange feature of phonetics.
There is a class of consonants that are "fricative": f, v, th, sh, s, z. In these consonants the mouth nearly closes so the air is forced through a narrow gap, making a hissing sound.
Two of these are classed as "sibilant": s and sh. The others are not sibilant, but there is no real reason why only s and sh are sibilant, that is just what the word means. It is used more by poets than by linguists. (As a poetic effect of using lots of words with the s or sh sound.)
The word "violet" has a non-sibilant fricative at the start and a stop consonant at the end. There is nothing here that could be called "sibilant" in any standard dialect. In particular, it is never pronounced "violets" or "violeth" in any standard dialect.
