1. [adv]  to a severe or serious degree; "fingers so badly frozen they had to be amputated"; "badly injured"; "a severely impaired heart"; "is gravely ill"; "was seriously ill"
2. [adv]  in a serious manner; "talking earnestly with his son"; "she started studying snakes in earnest"; "a play dealing seriously with the question of divorce"

SERIOUSLY is a 9 letter word that starts with S.