We found one dictionary that defines the word a wisp of a girl/boy:

General (1 matching dictionary)

1. a wisp of a girl/boy, a wisp of a girl/boy: Merriam-Webster

▸ Words similar to a wisp of a girl/boy ▸ Usage examples for a wisp of a girl/boy ▸ Idioms related to a wisp of a girl/boy ▸ Wikipedia articles (New!) ▸ Words that often appear near a wisp of a girl/boy ▸ Rhymes of a wisp of a girl/boy ▸ Invented words related to a wisp of a girl/boy