Dog Eat Dog Meaning

(idiomatic) Ruthlessly acquisitive or competitive. Describes a business or other set of circumstances where people try to succeed at the expense of other people.

Example:   In this company it's dog eat dog. If you don't do better than the rest, you're on the street in next to no time.
2007: Zoe Wood, Guardian Unlimited, Nov 11, Tesco has a flutter in Vegas.,
  It is dog eat dog on Las Vegas's world-famous Strip as casino complexes such as MGM Grand and New York New York compete for attention with outlandish gestures like rollercoaster rides and a replica of the Manhattan skyline.