Plagiarism is the theft performed anywhere on the internet for images, videos, writings etc and to post it anywhere under your ownership. Even paraphrasing is considered plagiarism because it has only the synonyms of the words used in the original writings present anywhere over the internet.
Understanding better:
"Plagiarism is presenting someone else’s work or ideas as your own, with or without their consent, by incorporating it into your work without full acknowledgement. All published and unpublished material, whether in manuscript, printed or electronic form." Source
I have read and understood the Complete steemit etiquette guide on Steemit Community and will do my best to embrace them.