Academics cannot agree on what constitutes plagiarism, according to new research.
A study by Diane Pecorari, senior lecturer in the School of Education at Malardalen University, Sweden, asked a sample of scholars to assess five plagiarised texts.
It identifies a marked lack of consistency in their views on what constitutes cheating.
The study, presented at the Fourth International Plagiarism Conference at Northumbria University last week, found that when a problem was identified, academics were reluctant to label it plagiarism, instead choosing words such as "unacceptable".
"The staff held extremely heterogeneous views about the examples and also had different explanations for those views. No two lecturers gave the same response," Dr Pecorari said.
She said the hesitancy could in part be explained by the "high stakes" involved in countries such as Sweden that class plagiarism as "cheating".
A student found guilty of such an offence could find their record tarnished well into their post-university career, she added.
But the different explanations given by participants in the study for finding, or failing to find, plagiarism also exposed a lack of common understanding, she argued.
In a bid to address the problem, academics in the US are attempting to draw up an international definition of plagiarism. Speaking at the conference, Teresa Fishman, director of the International Center for Academic Integrity at Clemson University in South Carolina, set out a model definition.
It rules that plagiarism occurs if an author "uses words, ideas or work products, attributable to an identifiable person or source, without attributing the work to the source from which it was obtained, in a situation in which there was a legitimate expectation of original authorship, in order to obtain benefit, credit or gain".
Dr Fishman said that plagiarism was not theft, copyright infringement or fraud, and should not be confused with poor citation skills.
Last month, Times Higher Education reported on plans for a national tariff covering penalties for student plagiarism in the UK that could be adopted internationally.