euphemism
/ˈju:fəmɪzəm; `jufəˌmɪzəm/ n[C, U]
(example of the) use of pleasant, mild or indirect words or phrases in place of more accurate or direct ones 委婉说法; 委婉话
`Pass away' is a euphemism for `die'. ｀去世＇是｀死＇的委婉说法.
`Pass water' is a euphemism for `urinate'. ｀小便＇是｀排尿＇的委婉语.