1. (verb)underscore, underline a line drawn underneath (especially under written matter) Synonyms: underline, underscore
2. (verb)underscore, underline, emphasize, emphasise give extra weight to (a communication) Synonyms: punctuate, underscore, stress, accent, emphasise, accentuate, underline, emphasize
3. (verb)underline, underscore draw a line or lines underneath to call attention to Synonyms: emphasise, underline, emphasize, underscore