From the U.S. Dept. of HHS Office of Research Integrity:
Research misconduct means fabrication, falsification, or plagiarism in proposing, performing, or reviewing research, or in reporting research results.
Fabrication is making up data or results and recording or reporting them.
Falsification is manipulating research materials, equipment, or processes, or changing or omitting data or results such that the research is not accurately represented in the research record.
Plagiarism is the appropriation of another person's ideas, processes, results, or words without giving appropriate credit.
Research misconduct does not include honest error or differences of opinion.