Final answer:
The incorrect use of "pineapple" instead of "pinnacle" by the chairman in a board meeting is an example of malapropism, which is a comic misuse of similar-sounding words.
Step-by-step explanation:
The use of the word "pineapple" instead of "pinnacle" is an example of malapropism. Malapropism is a figure of speech in which an incorrect word is used in place of a word with a similar sound, often leading to a nonsensical and humorous expression. This is different from a metaphor, an oxymoron, or hyperbole, which are other forms of figurative language. Metonymy and synecdoche are also different from malapropism as they involve a replacement that has a logical connection. In the case mentioned in the question, "pineapple" does not logically stand in for "pinnacle," and there is no intentional comparison being made, as would be the case in a simile.