TLDR: Self-actualisation is the goal of Maslow's Theory, not a need
As far as the needs are concerned, @jsakaluk's excellent, well supported answer to Is Maslow's hierarchy of needs really accurate at labeling sex as a physiological "need"? gave a good rundown of the definition.
Definitions of "Needs", "Motives", etc., are dime-a-dozen. Though I don't necessarily agree with all the ingredients, I like how well explicated the criteria by Baumeister and Leary (1995) are, according to whom a fundamental need should:
- produce effects readily under all but adverse conditions
- have affective consequences
- direct cognitive processing
- lead to ill effects (such as on health or adjustment) when thwarted
- elicit goal-oriented behavior designed to satisfy it (subject to motivational patterns such as object substitutability and satiation)
- be universal in the sense of applying to all people
- not be derivative of other motives
- affect a broad variety of behaviors
- have implications that go beyond immediate psychological functioning
We need to determine what self-actualisation actually is. Maslow described it as follows: (Maslow, 1943)
This term, first coined by Kurt Goldstein (1939), is being used in this paper in a much more specific and limited fashion. It refers to the desire for self-fulfillment, namely, to the tendency for him to become actualized in what he is potentially. This tendency might be phrased as the desire to become more and more what one is, to become everything that one is capable of becoming.
The specific form that these needs will take will of course vary greatly from person to person. In one individual it may take the form of the desire to be an ideal mother, in another it may be expressed athletically, and in still another it may be expressed in painting pictures or in inventions. It is not necessarily a creative urge although in people who have any capacities for creation it will take this form.
The clear emergence of these needs rests upon prior satisfaction of the physiological, safety, love and esteem needs. We shall call people who are satisfied in these needs, basically satisfied people, and it is from these that we may expect the fullest (and healthiest) creativeness (Kardiner, 1941). Since, in our society, basically satisfied people are the exception, we do not know much about self-actualization, either experimentally or clinically. It remains a challenging problem for research.
Maslow's hierarchy is visually put together as follows:
Image Source: Wikimedia Commons Under Creative Commons CC BY-SA 3.0)
and to attain the sixth level or stage: self-actualisation, is the goal of Maslow's Theory, not a need. Take away any of the levels below self-actualisation, and you will not reach the top goal. And as stated by Maslow (1943) — see above — and in the TLDR summary of @NickStauner's answer to Does evidence support Maslow's Hierarchy of Needs?,
One sequence can't fit all (it didn't claim to), but it makes sense in general, and so do the exceptions, and so do other motive models.
Maslow himself said:
Though, in principle, self-actualization is easy, in practice it rarely happens (by my criteria, certainly in less than 1% of the adult population. For this, there are many, many reasons at various levels of discourse, including all of the determinants of psychopathology that we not know. (Maslow, 2013)
also, the fact that "most of us function most of the time on a level lower than that of self-actualization" he called it the psychopathology of normality. (Loevinger, 1976)
Baumeister, R. F., & Leary, M. R. (1995). The need to belong: desire for interpersonal attachments as a fundamental human motivation. Psychological Bulletin, 117(3), 497-529.
DOI: 10.1037/0033-2909.117.3.497 PMID: 7777651
Goldstein, K. (1939). The organism: A holistic approach to biology derived from pathological data in man. Salt Lake City, UT: American Book Publishing.
Kardiner, A. B. R. A. M. (1941). The Traumatic Neuroses of War, New York: Paul B. Hoeber.
Loevinger, J. (1976) Ego Development: Conceptions and Theories (Jossey-Bass Behavioral Science Series). San Francisco, CA: Jossey-Bass Inc
Maslow, A. H. (1943). A theory of human motivation. Psychological Review, 50 (4), 370–96.
FREE via http://psychclassics.yorku.ca/Maslow/motivation.htm.
Maslow, A. H. (2013). Toward a psychology of being. Simon and Schuster [eBook].