A figure of speech in which a sensory experience is described in the terms of one of the other senses. Synesthesia is also know as "sense transfer" or the confusion of the senses.
There are certain descriptions that we generally think of as a visual image, others that we consider to be a sound or a taste. Writing synesthetic poetry is to decide to convince a reader otherwise. Generally sizzle is a sound, and aural image. Try to make your reader believe it is a flavor, or a color – it isn’t as hard as it sounds once you get the hang of it.
Since I said sizzle, we’ll go with sizzle, but this can be applied to nearly any sensory term you can think of.
Aural – The last errant drop of coffee sizzled on the burner.
Visual – She saw in the distance, through the sizzle of heat rising from the sand, a nomad atop a camel.
Sensory – She smiled knowingly at the sizzle of arousal that perked her nipples to attention.
Smell – She inhaled and the sizzle of ozone filled her nose, metallic and heavy.
Taste – After a month of fasting, he savored the sizzle of bacon on his tongue.
Pick a word, a sensation – any sensory image you can think of, and scramble it. Do something for your readers that most people don’t do, intrigue them. Give them a reaction they’d never otherwise have!