Sentence:  If we currently have any <WSD>borrows</WSD> of a value, we can't mutably borrow it into <code>self</code>, nor can we move it (because that would invalidate the existing <WSD>borrows</WSD>). 
Meaning of the word marked with <WSD> tags:  In the Rust programming language, the situation where the ownership of a value is temporarily transferred to another region of code.