IPA: /ˈdɛkstəˌrəsnəs/
KK: /ˈdɛkstəˌrəsnəs/
The quality of being skillful and quick in using the hands or body.
Her dexterousness allowed her to play the piano beautifully.
Dexterousness is formed from "dexter" (from Latin "dexter", meaning right or skillful) and the suffix "-ous" (meaning full of) combined with "-ness" (meaning a state or quality). The word describes the quality of being skillful or proficient, particularly with the hands.
Think of 'dexter' meaning skillful or right-handed, and remember that 'dexterousness' refers to the quality of being skillful.