underline verb
1 draw a line under a word
ADV. heavily The word ‘not’ was heavily underlined.
2 emphasize sth
ADV. clearly | just, merely, only, simply This disaster merely underlines the need for a consistent foreign policy. | further
VERB + UNDERLINE serve to | seem to | be intended to a move intended to underline US concern over the issue
PHRASES underline the fact that …
You can also check other dicts: underline (English, 中文解释 ), wordnet sense, Collins Definition