What do we mean by "critical thinking"?

Doesn't this concept involve a multitude of skills and attitudes?

You are absolutely right: It is an all-encompassing concept. Peter A. Facione reports on the results of a project that brought together experts from higher education and business to define critical thinking (see ERIC ED 315 423 and Critical Thinking: A Statement of Expert Consensus for Purposes of Educational Assessment and Instruction, Peter A. Facione, principal investigator, California Academic Press, Milbrae, CA 1990). Here is their consensus statement:

"We understand critical thinking to be purposeful, self-regulatory judgment which results in interpretation, analysis, evaluation, and inference, as well as explanation of the evidential, conceptual, methodological, criteriological, or contextual considerations upon which that judgment is based. CT is essential as a tool of inquiry. As such, CT is a liberating force in education and a powerful resource in one's personal and civic life. While not synonymous with good thinking, CT is a pervasive and self-rectifying human phenomenon. The ideal critical thinker is habitually inquisitive, well-informed, trustful of reason, open-minded, flexible, fair-minded in evaluation, honest in facing personal biases, prudent in making judgments, willing to reconsider, clear about issues, orderly in complex matters, diligent in seeking relevant information, reasonable in the selection of criteria, focused in inquiry, and persistent in seeking results which are as precise as the subject and the circumstances of inquiry permit. Thus, educating good critical thinkers means working toward this ideal. It combines developing CT skills with nurturing those dispositions which consistently yield useful insights and which are the basis of a rational and democratic society."