B1
to draw a line under a word or sentence, especially in order to show its importance
Dictionary examples:
The teacher underlined my name three times, asking, 'Who's this genius?' (0.0)
The boss underlined 'fun' in the company rules. Everyone was surprised! (0.0)
She underlined 'nap time' in her work schedule. Her boss wasn't amused. (0.0)
All the technical words have been underlined in red. (36.5)