Pronunciation: [ mal-uh-prop-iz-uhm ]
Definition: noun
an act or habit of misusing words ridiculously, especially by the confusion of words that are similar in sound

Origin: Mid 19th century; English
Etymology: from the name of the character Mrs Malaprop in Sheridan's play The Rivals (1775) + -ism
Usage:

Synonyms:
misapplication
misuse
Antonyms:
correct
praise
Example:
The young professional's malapropism made his manager chuckle when he said the "physical" versus "fiscal" year.