PP Morgan in his 1985 article about originality wrote "Originality, novelty and priority: three words to reckon with in scientific publishing"
A research is original if it is actaually conducted by a person who reported it. It is original if it is not plagiarized. It is original if it is based on sound methodology and the results are sound and the researcher discusses the results appropriately. It doesn't mean that it is a new noble discovery in a ceratain scientific discipline, as the definition of research doesn't necessarily imply that.
In peer review process, originality of research is evaluated using such criteris. You can look more information in the following links.
Similar question was raised by a fellow researcher a while ago. You can look at the discussion raised by RG community here https://www.researchgate.net/post/What_is_originality_in_research
Originality in research is a subject open to conflict of interpretation, as one' argument may be poised against the others'. However, there are generally acceptable guidelines pertaining ways in which a sound research should be carried out right from the inception of the idea to the to end. As observed with articles submitted to peer reviewed journals, despite similarities in research areas and topics, the submitted manuscripts are accepted and published based on a list of guidelines.
means a scientific work with at least one completely new / novel aspect or dimension.
For instance:
There are huge number of prior research and publications on the process of aging and
how to slow-down the process of aging and its effects. There are numerous publications on the usefulness of antioxidants in this regard and many literature on the usefulness of a particular antioxidant (e.g. Vitamin E) as an anti-aging molecule. Obviously repeating research work on these topics will not be ORIGINAL (although may have useful research results and enlighten some hidden aspects of the process. However, a study on a newly discovered derivative of Vitamin E and its effect on the process of aging (if not done before at all) will be an ORIGINAL SCIENTIFIC RESEARCH.
On the other hand:
An "original" research article is a detailed account of research activity written by the scientists who did the research - not by someone else who is reporting on the research; it is a primary resource. Some instructors may refer to these as "scientific research" articles or as "empirical" research.