Definition of "musingly"

It was half-way through the morning, and he had not breakfasted; the slight litter of other breakfasts stood about on the table to remind him of his hunger; and adding a poached egg to his order, he proceeded musingly to shake some white sugar into his coffee, thinking all the time about Flambeau.

1911, G. K. Chesterton, “The Blue Cross”, in The Innocence of Father Brown