Be lost in something Definition 1 of 3Pro Tip 1/3Deep Focus Indicates a person's complete attention in an activity to the point of unawareness of surroundings. He was lost in his painting for hours. Pro Tip 2/3Positive Escape Often implies a pleasant distraction from the real world. She was lost in her daydreams, smiling to herself. Pro Tip 3/3Emotional Subtext Can suggest deep emotions driving the focus, like passion or joy. The musician was lost in the melody, feeling every note.