cold fish definition by American Heritage Dictionary
noun InformalThe American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
An aloof person.
cold fish - Phrases/Idioms
A hard-hearted, unfeeling individual, one who shows no emotion, as in Not even the eulogy moved him; he's a real cold fish. This expression was used by Shakespeare in The Winter's Tale (4:4): “It was thought she was a woman, and was turn'd into a cold fish.” However, it came into wider use only in the first half of the 1900s.