"Dog eat dog" is analogous to the idiom "every man for himself", which implies a situation in which fierce deadly competition is necessary for your survival.
Some of these recent definitions seem to be offended at this saying due to their ignorance of the origin behind this 500 year old idiom. Some people do not seem to realize that this idiom is NOT meant to be taken literally. So, why is it called "dog eat dog" you may eagerly ask? Well, the idiom is actually a play on the much older latin idiom "dog does NOT eat dog" (canis caninam non est), which originated as early as 43 BC and first spoken by Roman scholar Marcus Tarentius Varro.
"Dog does not eat dog" is a proverbial saying indicating that even animals are better than humans in that they don’t prey on their own kind. The phrase entered into English discourse in 1543. Eventually, the phrase got flipped and applied to humans and henceforth "dog eat dog" was born. Both idioms generally imply the same thing (that humans are capable of being merciless).
So to summarize, the idiom "dog-eat-dog" is derived from its parent idiom "dog-does-not-eat-dog". The latter idiom makes sense in and of itself, while the former idiom ONLY makes sense in relation to its latter.
Case closed and dismissed.
Some of these recent definitions seem to be offended at this saying due to their ignorance of the origin behind this 500 year old idiom. Some people do not seem to realize that this idiom is NOT meant to be taken literally. So, why is it called "dog eat dog" you may eagerly ask? Well, the idiom is actually a play on the much older latin idiom "dog does NOT eat dog" (canis caninam non est), which originated as early as 43 BC and first spoken by Roman scholar Marcus Tarentius Varro.
"Dog does not eat dog" is a proverbial saying indicating that even animals are better than humans in that they don’t prey on their own kind. The phrase entered into English discourse in 1543. Eventually, the phrase got flipped and applied to humans and henceforth "dog eat dog" was born. Both idioms generally imply the same thing (that humans are capable of being merciless).
So to summarize, the idiom "dog-eat-dog" is derived from its parent idiom "dog-does-not-eat-dog". The latter idiom makes sense in and of itself, while the former idiom ONLY makes sense in relation to its latter.
Case closed and dismissed.
Me: It's a dog eat dog world out there.
Some kid: No it's not. It never was a dog eat dog world. Humans eat humans, but dogs don't eat dogs.
Me: My guy, you are so heavily misinformed. Dog eat dog isn't referring to dogs, it's referring to humans.
Some kid: So why don't they just name it "human eat human" instead?
Me: Because context my guy, it's all about context. You see... "dog eat dog" actually belongs to the much older idiom "dog does not eat dog", indicating that dogs never prey on their own kind. It took around 700 years for this idiom to become flipped and applied to humans. And if it weren't applied to humans, well, that would completely negate the original meaning as that would imply dogs are merciless in which they aren't (most animals will back down from a fight if they lose, humans don't).
Some kid: No reply.
Me: Also since you took it literally, I'll have you know that from an evolutionary standpoint, dogs will eat other dogs if this is what ensures their survival.
Some kid: No it's not. It never was a dog eat dog world. Humans eat humans, but dogs don't eat dogs.
Me: My guy, you are so heavily misinformed. Dog eat dog isn't referring to dogs, it's referring to humans.
Some kid: So why don't they just name it "human eat human" instead?
Me: Because context my guy, it's all about context. You see... "dog eat dog" actually belongs to the much older idiom "dog does not eat dog", indicating that dogs never prey on their own kind. It took around 700 years for this idiom to become flipped and applied to humans. And if it weren't applied to humans, well, that would completely negate the original meaning as that would imply dogs are merciless in which they aren't (most animals will back down from a fight if they lose, humans don't).
Some kid: No reply.
Me: Also since you took it literally, I'll have you know that from an evolutionary standpoint, dogs will eat other dogs if this is what ensures their survival.
by Mary Mary Quite The Contrarian August 3, 2021
Get the Dog eat dogmug. 
Bobby-ur mum gay lol
Charlie-ur dog likes the clog
Dog wails and demonic sounds in the distance as all dogs are dragged into hell
Charlie-ur dog likes the clog
Dog wails and demonic sounds in the distance as all dogs are dragged into hell
by Agiantbraintumor May 15, 2018
Get the ur dog likes the clogmug. An insult used irritate players in competitive gaming. Usually used by children under 13, or toxic teenagers.
"Dog Water" Is repeated multiple times in a sentence.
"Dog Water" Is repeated multiple times in a sentence.
by TheReallyFady1 March 31, 2021
Get the Dog Watermug. by Slimelife dre May 9, 2021
Get the Dog assmug. by RD_ May 16, 2022
Get the dan the dogmug. a domesticated carnivorous mammal that typically has a long snout, an acute sense of smell, non-retractable claws, and a barking, howling, or whining voice
That is a Funny Looking Dog
by the pelipper that eat pepsi March 12, 2022
Get the Dogmug.