CATACHRESIS [Stress: ‘kata-KREE-sis’]. A traditional term for the mistaken use of one word for another, as in Royal Anglican Regiment for Royal Anglian Regiment. An actual or assumed MISTAKE of this kind may cause confusion and resentment, and lead to controversy, as with the use of disinterested where uninterested might be more appropriate. Occasionally, catachresis can lead to the supplanting of one word by another: for example, humble for umble in the phrase humble pie. Such a pie was originally made from umbles (the innards of a deer) and was so recognized until the 19c. The OED records humble pie from 1648, and the figurative usage eating humble pie from 1830. In the 20c, only the figurative use occurs and there is therefore no confusion or resentment. By and large, catachresis arises when words are similar in form, as with militate and mitigate (‘His book was always likely to be serious, which might have mitigated against a large sale,’ Sunday Times, 17 Dec. 1989), or have a converse relationship, as with learn and teach, imply and infer, in which case one word may take over both senses (Learn Yourself Scouse: book title; Are you inferring I don't know what I am doing?). Confusion over such words can persist for centuries and is a popular topic in usage books and letters to editors. The term is neutral in PHILOLOGY but often pejorative in general use. See CONFUSIBLE, HOWLER, MALAPROPISM, SEMANTIC CHANGE.

cat·a·chre·sis / ˌkatəˈkrēsis/ • n. (pl. -ses / -sēz/ ) the use of a word in a way that is not correct, for example, the use of mitigate for militate.DERIVATIVES: cat·a·chres·tic / -ˈkrestik/ adj.

catachresis improper use (of word). XVI. — L. catachrēsis — Gr. katákhrēsis, f. katakhrêsthai use amiss, f. CATA- 3 + khrēsthai use.
So catachrestic(al) adjs. XVII.