English Grammar: Figure of Speech
A Figure of Speech is where a word or words are used to create an effect, often where they do not have their original or literal meaning.
If someone says that they are 'starving', they do not mean that they are in fact dying of hunger, but that they are very hungry. This is a simple example of a figure of speech, where the word is used to heighten or increase the state that they are describing. A metaphor or a simile are two of the most common forms used.