Source : Webster's Revised Unabridged Dictionary (1913)

Sincerely \Sin*cere"ly\, adv.
   In a sincere manner. Specifically:
   (a) Purely; without alloy. --Milton.
   (b) Honestly; unfeignedly; without dissimulation; as, to
       speak one's mind sincerely; to love virtue sincerely.

Source : WordNet®

sincerely
     adv 1: with sincerity; without pretense; "she praised him sincerely
            for his victory"; "was unfeignedly glad to see his old
            teacher"; "we are truly sorry for the inconvenience"
            [syn: {unfeignedly}, {truly}] [ant: {insincerely}]
     2: written formula for ending a letter [syn: {sincerely yours}]