What is the meaning of Selfish?

(clarification of this definition is needed)(The addition of quotations indicative of this usage is being sought:) Holding one's own self-interest as the standard for decision making.

Having regard for one's own well-being above that of others.

Of video game characters: relying on their own actions and capabilities to be effective in the game, rather than on other characters.

Related to or equivalent to a selfish gene; best understood as existing to preserve and replicate itself in competition with other entities at the same level of existence, rather than at the level of the individual or population containing it.

Source: wiktionary.org