Is copying lab results a form of plagiarism? A quick question, which I'm asking out of curiosity rather than an actual problem.

Plagarism and how to detect/combat/punish it seems to be a common topic on this SE. When I was an undergraduate, 20 years ago, I don't remember ever plagerising a book or other student, or any of my classmates doing the same (at least not that I knew of).

However, I did a practical science in which we had 1 or 2 full-day lab workshops every week. It was very common for most of the students in these labs not to get the "expected" result, due largely to inexperience and poor technique. It was equally common for all the students to then copy, and subtly modifiy, the results of the few students who did get it to work. They would then independently use this in writing up the assignments by themselves.

Would this be considered a form of plagerism in a modern academic environment? If so, what should science students with poor practical results do to write up their assignments?

EDIT: after comments, I feel compelled to make clear these were undergraduate labs with previously verified results. We were not undermiming scientific process here.
Plagiarism is typically defined in terms of taking the work of another person and passing it off as your own (see, e.g., the Wikipedia page).  It does not matter whether the material that you steal is words, data, pictures, etc.

Thus, I would classify the practice of copying lab results that you describe as plagiarism.  It could also be categorized as other types of academic dishonesty as well, such as falsification of experimental results.