sick as a dog, to be

*sick as a dog

Cliché very sick; sick and vomiting. (*Also: as ~.) We've never been so ill. The whole family was sick as dogs. Sally was as sick as a dog and couldn't go to the party.
See also: dog, sick
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.

sick as a dog

Very ill, especially from a stomach malady. For example, I don't know what was in that stew but I was sick as a dog all night. This simile was first recorded in 1705. Why a dog should be viewed as particularly sick remains unclear.
See also: dog, sick
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

sick as a dog

If you are as sick as a dog, you are very ill. The last time I ate shellfish I was sick as a dog for 48 hours afterwards.
See also: dog, sick
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012

sick as a dog

extremely ill. informal
See also: dog, sick
Farlex Partner Idioms Dictionary © Farlex 2017

(as) sick as a ˈdog

(informal) feeling very ill; vomiting a lot: I was sick as a dog last night.
See also: dog, sick
Farlex Partner Idioms Dictionary © Farlex 2017

sick as a dog, to be

To feel very ill, particularly to feel nauseated. Despite being touted as man’s best friend, dogs are often maligned. This proverbial simile dates from the sixteenth century or earlier and is still current. Occasionally it has appeared with sick meaning “tired of,” as by David Garrick (Neck or Nothing, 1766, 1:1): “I am sick as a dog of being a valet.”
See also: sick
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer
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