What is "catachresis"

Catachresis \Cat`a*chre"sis\, n. [L. fr. Gr. ? misuse, fr. ? to misuse; kata` against + ? to use.] (Rhet.) A figure by which one word is wrongly put for another, or by which a word is wrested from its true signification; as, ``To take arms against a sea of troubles''.
--Shak. ``Her voice was but the shadow of a sound.''
--Young.

1580s, from Latin catachresis, from Greek katakhresis "misuse" (of a word), from katakhresthai "to misuse," from kata- "down" (here with a sense of "perversion;" see cata-) + khresthai "to use" (see hortatory). Related: Catachrestic; catachrestical; catachrestically.

n. 1 A misuse of a word; an application of a term to something which it does not properly denote. 2 (context rhetoric English) A misapplication or overextension of figurative or analogical description; a wrongly-applied metaphor or trope.

n. strained or paradoxical use of words either in error (as `blatant' to mean `flagrant') or deliberately (as in a mixed metaphor: `blind mouths')

Catachresis (from Greek , "abuse"), originally meaning a semantic misuse or error—e.g., using "militate" for "mitigate", "chronic" for "severe", "anachronism" for "anomaly", "alibi" for "excuse", etc.—is also the name given to many different types of figure of speech in which a word or phrase is being applied in a way that significantly departs from conventional (or traditional) usage.