cosh

UK: /ˈkɒʃ/ US: (kosh)

WordReference Random House Unabridged Dictionary of American English © 2026

cosh¹  (kosh), [Chiefly Brit. Slang.]
n. 

1. British Terms a blackjack;
   bludgeon.

v.t. 

2. British Terms to hit on the head with a cosh.

• Romany kosh, koshter stick
• perh. 1865–70

cosh²  (kosh), n. [Math.]

1. Mathematics hyperbolic cosine.

• cos(ine) + h(yperbolic) 1870–75

Collins Concise English Dictionary © HarperCollins Publishers::

cosh / kɒʃ/ noun

1. a blunt weapon, often made of hard rubber; bludgeon
2. an attack with such a weapon

verb (transitive)

1. to hit with such a weapon, esp on the head

Etymology: 19th Century: from Romany kosh, from koshter skewer, stick

cosh / kɒʃ ˈkɒsˈeɪtʃ/ noun

1. hyperbolic cosine; a hyperbolic function, cosh z = (e^z + e^–z), related to cosine by the expression cosh iz = cos z, where i = √–1

Etymology: 19th Century: from cos( ine) + h( yperbolic)