1. a substance or product used to make something lighter in color or shade
2. something that makes a load or burden less heavy

Examples

• She used a hair lightener to achieve blonde highlights.
• The fabric lightener removed the dark stains from the curtains.
• This skin lightener helps reduce the appearance of age spots.
• The new backpack design includes a lightener frame to reduce weight.
• Wood lightener can restore the natural color of weathered furniture.
• The photographer used a lightener to brighten the shadows in the portrait.