In my definition I would define it as having poor sportsmanship in the means of not taking responsibility or ownership.
It can be intentionally or unintentionally, but one way or the other it’s not fair to others and other people may suffer from such behaviour.
When things turn out to be favourable, a person may take all the credit and believe that he/she is the core reason of making it happen; however on the contrary, when things go south it will always seem to be of other people’s fault and he/she will not take the blame and feels that he/she is “unfortunate” of other people’s actions.
I have seen too many people with such behaviour; that being said, it can happen unintentionally as someone may just didn’t take the time to look into the big picture and got blindsighted. This doesn’t excuse a person for his/her actions though.