1. to cause (a camera, lens, or optical instrument) to lose focus; to make an image blurry or unclear
Usage: third-person singular present tense or plural form of 'defocus'; British spelling uses double 's'; American spelling typically uses single 's' (defocuses)
2. to distract or divert attention away from something; to reduce concentration or emphasis
Usage: figurative or metaphorical use

Examples

• The photographer accidentally defocusses the camera when adjusting the lens.
• Moving the lens too quickly defocusses the image on the screen.
• Excessive noise defocusses the students from their work.
• The bright light defocusses your attention from the main subject.
• She defocusses the microscope to examine the specimen at a different depth.
• Poor lighting defocusses the viewer's ability to see fine details.