What is "intelligence" in "artificial intelligence"? As far as Artificial Intelligence is concerned, what is "intelligence"? The definition I see on various sites like Wikipedia:       


  Intelligence has been defined in many different ways including as one's capacity for logic, understanding, self-awareness, learning, emotional knowledge, planning, creativity, and problem solving          


Merriam Webster: 


  
  The ability to learn or understand or to deal with new or trying situations :  reason; also :  the skilled use of reason.     
  The ability to apply knowledge to manipulate one's environment or to think abstractly as measured by objective criteria (such as tests).
  


etc seem to be a bit broad and nebulous, and not necessarily what I would be thinking of if I wanted to build an AI, or evaluate the intelligence of non human life-forms.            

The definition I currently go with is:         


  General problem solving ability.            


However, I'm not sure if this is broad enough to encompass all we think of when we say "intelligence" in the context of AI, or what we would be looking for in "intelligent" life-forms. What's a useful definition of intelligence. Broad enough to encompass all the we consider when we think intelligence, yet narrow enough to exclude particular idiosyncrasies of specific intelligent agents? A universal definition of intelligence applicable to all intelligent agents.
This is a very broad and not well defined issue, but two theories that may help you to get a better understanding are the following :

Triarchic theory of intelligence by Robert J. Sternberg


  Sternberg's definition of human intelligence is "(a) mental activity
  directed toward purposive adaptation to, selection and shaping of,
  real-world environments relevant to one's life" (Sternberg, 1985, p.
  45).


Sternberg divides intelligence into three major subtheories:


  Componential – analytical subtheory
  
  Analytical giftedness is influential in being able to take apart
  problems and being able to see solutions not often seen.
  Unfortunately, individuals with only this type are not as adept at
  creating unique ideas of their own.
  
  Experiential – creative subtheory
  
  Sternberg splits the role of experience into two parts: novelty and
  automation. A novel situation is one that you have never experienced
  before. People that are adept at managing a novel situation can take
  the task and find new ways of solving it that the majority of people
  would not notice (Sternberg, 1997). A process that has been automated
  has been performed multiple times and can now be done with little or
  no extra thought. Once a process is automatized, it can be run in
  parallel with the same or other processes.
  
  Practical – contextual subtheory
  
  Sternberg's third subtheory of intelligence, called practical or
  contextual, "deals with the mental activity involved in attaining fit
  to context" (Sternberg, 1985, p. 45). Through the three processes of
  adaptation, shaping, and selection, individuals create an ideal fit
  between themselves and their environment. This type of intelligence is
  often referred to as "street smarts." Adaptation occurs when one makes
  a change within oneself in order to better adjust to one's
  surroundings (Sternberg, 1985). For example, when the weather changes
  and temperatures drop, people adapt by wearing extra layers of
  clothing to remain warm.


Theory of multiple intelligences by Howard Gardner


  The theory of multiple intelligences differentiates intelligence into
  specific 'modalities', rather than seeing intelligence as dominated by
  a single general ability. Howard Gardner proposed this model in his
  1983 book Frames of Mind: The Theory of Multiple Intelligences.
  According to Gardner, an intelligence must fulfill eight criteria:
  musical-rhythmic, visual-spatial, verbal-linguistic,
  logical-mathematical, bodily-kinesthetic, interpersonal,
  intrapersonal, and naturalistic. He later suggested that existential
  and moral intelligence may also be worthy of inclusion.