"underlines" in the noun sense
1. underscore, underline
a line drawn underneath (especially under written matter)
"underlines" in the verb sense
1. underscore, underline, emphasize, emphasise
give extra weight to (a communication
"Her gesture emphasized her words"
2. underline, underscore
draw a line or lines underneath to call attention to
Source: WordNet® (An amazing lexical database of English)
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