The definition of girlish is something related to or characteristic of a young woman or girl.
A little, high-pitched giggle like you would expect a young girl to have is an example of a girlish giggle.
of, like, or suitable to a girl or girlhood
Characteristic of or befitting a girl: girlish charm.
(comparative more girlish, superlative most girlish)
girl + -ish