with only a small amount of weight or force [= gently]:
I knocked lightly on the door.
using or having only a small amount of something:
a lightly greased pan
lightly armed soldiers
to do something without serious thought:
Divorce is not a matter you can afford to take lightly.
4 also be let off lightly
to be punished in a way that is less severe than you deserve:
He got off lightly because his father was a lawyer.
without worrying, or without appearing to be worried:
'Things will be fine,' he said lightly.