American Heritage Dictionary
(1)
Century Dictionary
(1)
GNU Webster's 1913
(1)
WordNet
(2)
Elsewhere on the web
"Tiffany," Nixon makes creating great music sound effortless -- what more could you ask for from a debut single?— Poster Girl
Although losing weight is not effortless, the prolonged outcomes brought in by it would in all likelihood be of assistance to any dieter considering to shake off those unwished and bad pounds— Find Free Articles - ArticlesBase
His writing was so effortless, his sense of humor and observation so pitch-perfect, there was really nobody who came close.— The Rap Sheet

Century Dictionary (1)
Bubble size: how much this word was used in a year
Bubble height: used more or less than expected, vs. all uses evenly distributed
You can expect to see this word about twice a month.