metaphor vs plain speech

metaphor

verb
  • To use a metaphor. 

  • To describe by means of a metaphor. 

noun
  • The use of a word or phrase to refer to something other than its literal meaning, invoking an implicit similarity between the thing described and what is denoted by the word or phrase. 

  • A word or phrase used in such implied comparison. 

  • The use of an everyday object or concept to represent an underlying facet of the computer and thus aid users in performing tasks. 

plain speech

How often have the words metaphor and plain speech occurred in a corpus of books? (source: Google Ngram Viewer )