Catachresis is a very formal way of saying 'mistake' about a use of words. OED defines it as "Improper use of words; application of a term to a thing which it does not properly denote; abuse or perversion of a trope or metaphor." It is conventionally listed as a figure of speech, although it is not use as a deliberate choice in language.
The word is probably unnecessary for most students. Say 'mistake' or 'error', or 'wrong usage'. Teachers may just underline the word that is wrongly used.
Catachresis is a noun. The associated adjective is catachrestic. Pronounce them as 'cat-er-KREES-is' (IPA: /kæt ə ˈkriːs ɪs/) and 'cat-er-KREES-tick' (IPA: /kæt ə ˈkriːs tɪk/) OR 'cat-er-CRESS-tick' (IPA: /kæt ə ˈkrɛs tɪk/).
Etymological note: The English word catachresis is a transliteration of the Greek word κατάχρησις (katachrēsis), a noun from the verb καταχράομαι (katachraomai), which means 'I make full use of, I use up, I misuse or abuse'. The philosopher Aristotle (384-322 BCE) uses the verb several times in connection with the misuse or misapplication of a word.