Antonyms of adj effortful

1 sense of effortful

Sense 1
effortful (vs. effortless) -- (requiring great physical effort)

effortless (vs. effortful) -- (requiring or apparently requiring no effort; "the swallows glided in an effortless way through the busy air")
        => facile -- (performing adroitly and without effort; "a facile hand")
        => unforced, unstrained -- (not resulting from undue effort; not forced; "a voice with a pleasingly unforced quality"; "his playing is facile and unstrained")

Similarity of adj effortful

1 sense of effortful

Sense 1
effortful (vs. effortless) -- (requiring great physical effort)
       => arduous, backbreaking, grueling, gruelling, hard, heavy, laborious, operose, punishing, toilsome -- (characterized by effort to the point of exhaustion; especially physical effort; "worked their arduous way up the mining valley"; "a grueling campaign"; "hard labor"; "heavy work"; "heavy going"; "spent many laborious hours on the project"; "set a punishing pace")
       => dragging -- (marked by a painfully slow and effortful manner; "it was a strange dragging approach"; "years of dragging war")
       => exhausting, tiring, wearing, wearying -- (producing exhaustion; "an exhausting march"; "the visit was especially wearing")
       => heavy, labored, laboured -- (requiring or showing effort; "heavy breathing"; "the subject made for labored reading")
       => labor-intensive, labour-intensive -- (requiring a large expenditure of labor but not much capital; "cottage industries are labor intensive")
       => leaden, plodding -- ((of movement) slow and laborious; "leaden steps")
       => Sisyphean -- (both extremely effortful and futile)
       => arduous, straining, strenuous -- (taxing to the utmost; testing powers of endurance; "his final, straining burst of speed"; "a strenuous task"; "your willingness after these six arduous days to remain here"- F.D.Roosevelt)
          Also See-> difficult#1, hard#1