Random House (1991):
Science: a branch of knowledge or study dealing with a body of facts or truths systematically arranged and showing the operation of general laws; systematic knowledge of the physical or material world gained through observation and experimentation; any of the branches of natural or physical science; systematized knowledge in general; knowledge, as of facts or principles; knowledge gained by systematic study; a particular branch of knowledge; any skill or technique that reflects a precise application of facts or principles
Ackoff (1962, p 1):
The extensive literature addressed to the definition or characterization of science is filled with inconsistent points of view and demonstrates that an adequate definition is not easy to attain. Part of the difficulty arises from the fact that the meaning of science is not fixed, but is dynamic. As science has evolved, so has its meaning. It takes on new meaning and significance with successive ages. This evolution is not to be stopped by the act of defining.
Curtis (1979, p 13):
Science, biological and other, is a way of seeking principles of order in the natural world. Art is another, as are religion and philosophy. Science has two separate components: (1) objective evidence based on observation or experiment or a combination of the two - the data - and (2) the structuring of data by making meaningful connections among them. The great discoveries in science are not merely the addition of new facts but the perception of new relationships among the available facts, in other words, the development of new concepts and new ideas...
A modern science is not a static accumulation of facts organized in particular way, but a somewhat amorphous body of knowledge that not only constantly grows, developing new bulges and unpredictable appendages, but also may suddenly change its entire shape. Science is dynamic, not static; consequently it cannot be contained within textbooks or libraries or information retrieval centers, but rather it is a process taking place in the minds of living scientists.
Masterman (1970):
Far from querying the existence of Kuhn's 'normal science', I am going to assume it. There is no need to keep on invoking history here. That there is normal science - and that it is exactly as Kuhn says it is - is the outstanding, the crashingly obvious fact which confronts and hits any philosophers of science who set out, in a practical or technological manner, to do any actual scientific research. It is because Kuhn - at last - has noticed this central fact about all real science (basic research, applied, technological, are all alike here), namely that it is normally a habit-governed, puzzle-solving activity, not a fundamentally upheaving or falsifying activity (not, in other words, a philosophical activity), that actual scientists are now, increasingly reading Kuhn instead of Popper: to such an extent, indeed, that, in new scientific fields particularly, 'paradigm' and not hypothesis' is now the 'O.K. word'. It is thus scientifically urgent, as well as philosophically important, to try to find out what a Kuhnian paradigm is. (ibid., p 60)
When 'normal science' sets in, anywhere, there you have science, and where it does not set in, there you have philosophy or something else, not science... (ibid., p 75)
Sanitt (1996)
perceives science as a problem-generating activity rather than a problem-solving one. He suggests that we should perceive "science as a questioning procedure providing a heuristic pattern to an otherwise unplanned search for truth" (Sanitt 1996, p 40).
Also see Rosen (1996).