Paraphrasing is finding another way to say something when you don't know how to say it. Paraphrasing is not only an essential skill for all speakers but also key to learners developing communicative ability beyond their existing knowledge of language.
The learner is describing a photograph of a glider and doesn't know the word, so paraphrases by saying ‘an airplane that uses the wind'.
In the classroom
One way to practise paraphrasing is through word games. For example, in a definition game learners have to provide paraphrases, so that others can guess the original word. This can be done in written form in crossword activities as well.