Antonyms of adj methodical

1 sense of methodical

Sense 1
methodical -- (characterized by method and orderliness; "a methodical scholar")

INDIRECT (VIA organized) -> disorganized, disorganised -- (lacking order or methodical arrangement or function; "a disorganized enterprise"; "a thousand pages of muddy and disorganized prose"; "she was too disorganized to be an agreeable roommate")

Similarity of adj methodical

1 sense of methodical

Sense 1
methodical -- (characterized by method and orderliness; "a methodical scholar")
       => organized (vs. disorganized) -- (methodical and efficient in arrangement or function; "how well organized she is"; "his life was almost too organized")