What does "slightness" mean?

The property of being slight, smallness, petiteness

What is a synonym for "slightness"?

Common synonyms include: slenderness, airiness, austerity, big deal, collapse, daintiness.

noun

noun ·Moderate ·College level

Noun

1
The property of being slight, smallness, petiteness
"Poor nutrition explained his slightness."
2
the property of an attractively thin person wordnet
3
slenderness wordnet
4
the quality of being unimportant and petty or frivolous wordnet

"Poor nutrition explained his slightness."

From slight + -ness.