The field of non-literal language is vast - it's one of those areas where the more you look for, the more you find. I have to use a negative nametag for it just because it is so big. Nonliterals applied to lit crit refers to the entire pantechnicon of description through analogy or imagery.
Broadly speaking, nonliterals can be divided into two categories, which, whatever you call them, are either local or general. Local nonliterals are those confined to single phrase or sentence, and the most familiar of these are simile and metaphor.
This includes everything from the mildly metaphorical - 'we're having mild weather' - through improbable simile - 'as obvious as a lead brick in a bowl of rice pudding' - to extreme mixed metaphor - 'his whole body was a sword which sang like a ribbon in the wind'.
General nonliterals are those that spread through a whole paragraph or engulf an entire novel. Symbolism is the most frequently named of these, and - though it's forms can be as myriad as your imagination - is one of the easiest to describe. Symbolism is the repeated use of symbols to evoke or enhance a particular theme or characteristic. Symbols are generally images but sometimes gestures or sounds, which carry a specific meaning. Imagery can be used symbolically, through repetition, such as associating a particular symbol with a particular character or type of event.
I have so much material on this stuff that I will be posting examples of the above, and more, in future posts. I had meant to devote this post to the following:
Those who know their Latin will know that classical Latin is a vocab-poor language. There are very few actual words in it, compared with modern languages. This is because the authors of the Classical Roman period deliberately restricted themselves to words of known Latin origin when writing and orating. So, when they had to describe a concept for which there was no single word, rather than neologising, they would prefer to use metaphor. A familiar example might be campus martius - a battlefield (also a fairly ubiquitous place name). Campus is a field, martius "of Mars" (the Romans' god of war). Indeed Caesar uses the this and that of Mars to describe all sorts of military matters, and I remember an example (those more learned than me can perhaps confirm whether it is Caesar or someone else) describing 'Mars moving among the armies on the field' as a way to convey the currents of activity on the battlefield.
I gave the example mild above because the expression mild weather, and its much less used counterpart inclement weather are fine examples of unwitting metaphor. This usage of mild in modern English is so familiar that it doesn't occur to most of us, meteorological anthropomorphism notwithstanding, that it is a metaphor. But mild means gentle, kind or merciful.
We generally describe as cliché*, any simile or metaphor that is so familiar that we tend to use it automatically ('rooted to the spot'), however it isn't general used for those single word examples like mild that have become so familiar (Doug Harper says that the earliest usage for weather is 14th century).
The writer ought to be aware of when he is using them. The editor has to be sensitive to every single one.
*I will be coming back to this
Yes, I am really pleased with 'meteorological anthropomorphism notwithstanding' !