slighten

To make or become slight; make or become less pronounced, less noticeable, or less obvious.

His smile slightened as if he knew they talked of him.

With tissue I softened my rouge, slightened my lipstick; studying my redesigns in my green compact's mirror I marveled, seeing yet another strange face.

To slight.

[…] as God forbid that anyone should hint a slightening word of what our sons and brothers are doing just now, and doing for us!

They may take ill or feel slightened for not having been approached directly.

To level out, smooth, or flatten.

to slighten the sheets out