Source : Webster's Revised Unabridged Dictionary (1913)

Gravely \Grave"ly\, adv.
   In a grave manner.

Source : WordNet®

gravely
     adv 1: in a grave and sober manner; "he walked soberly toward the
            altar" [syn: {soberly}, {staidly}]
     2: 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"
        [syn: {badly}, {severely}, {seriously}]