Source : Webster's Revised Unabridged Dictionary (1913)

Effortless \Ef"fort*less\, a.
   Making no effort. --Southey.

Source : WordNet®

effortless
     adj 1: requiring or apparently requiring no effort; "the swallows
            glided in an effortless way through the busy air"
            [ant: {effortful}]
     2: not showing effort or strain; "a difficult feat performed
        with casual mastery"; "careless grace" [syn: {casual}]